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NOTES 



ON 



MECHANICAL DRAWING 



PREPARED FOR THE USE OF 
STUDENTS IN 



MECHANICAL, ELECTRICAL AND 
CHEMICAL ENGINEERING 



AT THE 



UNIVERSITY OF PENNSYLVANIA 



V BY 
HORACE P. FRY, B. S. in E. E. 

ASST. PROF. OF MECHANICAL DRAWING 



PHILADELPHIA 

1916 



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COPYRIGHT, 1916, 

BY 

HORACE P. FRY 



FIFTH EDITION. 



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m 28 1917 
©C1A460505 



PREFACE. 

Mechanical drawings are required in all constructive work 
and, as the name implies, are made with precision instruments. 
In making such drawings, strict adherence to the principles of 
projection, accuracy and neatness in execution remove all doubts 
as to what is intended and make a drawing perfectly clear to all 
accustomed to reading and working from them. 

The student should realize that the user of a drawing con- 
structs as the drawing shows, not as the one who made the 
drawing intended to show. 

The matter contained in these Notes is not an exhaustive 
treatise on mechanical drawing, but is intended to supplement 
class instruction. 

These Notes contain recognized standards, conventions and 
technic used in American practice, together with tables and other 
information valuable in drawing. 

Questions are continually arising in a student's mind as to 
just how to represent certain conditions, and since he will remember 
longer that which he looks up for himself, it is his duty to answer 
these questions by referring to the standards, conventions and 
technic of practice before questioning his instructor. 

The previous editions of the Notes were developed along 
lines suggested by students' questions. 

The present edition has been enlarged along the same lines. 
Part of the subject matter has been rewritten to increase its scope. 

The numbering of the paragraphs under each topic provides 
a ready reference for the student's attention relative to errors in 
his work and for study or other assignment. 

The topic headings and the more important features under 
each have been emphasized by bold -face type. 

The lack of complete uniformity in all lines of work using 
mechanical drawings makes it impossible to include in these Notes 
anything except fundamentals. 

H. P. F. 
Philadelphia, Pa. 

September, 1916. 

(3) 



CLASSIFICATION OF DRAWINGS. 



1. DRAWINGS are divided into two classes — those made 
purely freehand and those made with instruments of precision. 

2. FREEHAND DRAWINGS are made for artistic effects, 
historical records or the purpose of registering mental pictures. 
They show only that which is visible and are readily understood. 

3. FREEHAND SKETCHES for constructive purposes are 
made with few or no instruments, but in other respects they are 
the same as a mechanical drawing. 

4. MECHANICAL DRAWINGS are made with instruments 
of precision to convey, from one person to another, complete 
and accurate information of the visible and invisible structure 
of an object, not necessarily of a mechanical nature. They are 
made according to definite principles of projection and are fully 
understood only by those who have been trained in this so-called 
"graphic language." 

5. GEOMETRICAL DRAWINGS are made with instruments 
and involve the principles of Geometry in solving problems. A 
knowledge of these principles is valuable and fundamental, but 
very few of them are used, since any one making a Mechanical 
Drawing has at his command instruments for obtaining the same 
results by quicker means. For example, drawing lines parallel, 
erecting perpendiculars and drawing arcs (fillets) tangent to lines. 

ESSENTIALS. 1. A designer, in any line of work, uses draw- 
ing as the means of expressing his ideas. 

2. The aim in learning how to draw is to acquire the ability 
to express ideas graphically, so they may be put into concrete 
form for use. 

3. In making a mechanical drawing the draftsman (meaning 
anyone making the drawing) should remember that accuracy^ 
clearness, neatness, correctness in dimensioning, necessary notes 
and a proper title are all essential to the working value of the 
drawing, since the object of such a drawing is to enable one to 
make that which has been pictured without recourse to any other 
information than that contained on the drawing. The artisan 
constructs as the drawing shows, not as the draftsman may have 
intended to show. 

(4) 



INSTRUMENT LIST. 



1. THE MATERIALS SPECIFIED are standard and repre- 
sentative types used in good practice. A novice should consult 
his instructor before making any substitutions until he learns 
that the best are cheapest in the end. 

2. THE COMPLETE EQUIPMENT should be at hand at 
all times, and must contain the following: (consumed, broken 
and lost portions to be replaced at once) . 

A. One set of Drawing Instruments in a morocco-covered case 
having two metal hinges and clasps (see Fig. 1), the set to 
include 

5i" compass, pen, pencil and lengthening bar, fixed 

needle point leg. 
3 J" bow spacer. 

3i" bow pencil with needle point. 
3|" bow pen with needle point. 
5 " ruling pen. 
Nickel-plated lead case. 

[Set No. 2050, made by Theodore Alteneder & Sons, 
Philadelphia.] 




Fi(i. 1. 



B. 



C. 
p. 



Triangular Box-wood scale having the following scak\s thereon: 
12'^^ iy^ 6", 4^ 3^ 2^ \Y to the foot, and 50 parts to the 
inch divided tlie full length of the scale. 
One 8"— 45° celluloid triangle. Not less than ,\" thick. 
One 12'^— 60° celluloid triangle. Not less than ^^" thick. 

(5) 



G. 

H. 
I. 

J- 
K. 
L. 



N 



O. 
P. 

Q. 

R. 




E. One celluloid irregular curve, as shown in Fig. 2. (K. and E. 

No. 19.) 

F. T square, 30" blade (not set in head). 

Blade to have celluloid edges tongued 

and grooved to wood. 
Two 6H drawing pencils. (Kooh-i-noor, 

Van Dyke, Cast ell or Venus.) 
One small ink eraser. (E. Faber's improved.) 
One large pencil eraser. (E. Faber's ruby or green.) 
One Art Gum cleaning rubber (large) . 
One dozen |" thumb tacks. (Thin head, K. & E. Ideal.) 
Two sheets 11" x 30" drawing paper. (K. & E. Normal.) 
M. Reinhardt's Freehand Lettering, for Draftsmen, Engineers and 

Students. 
Drawing board, white pine, IV x 31" with cleats on the back; 

face of board must not be shellacked. Each cleat to have a 

3" X -^" slot cut through next to board. Slots must be 

in line and about central of the cleats. 
One bottle of black waterproof drawing ink. Higgins'. 
One erasing shield. Must not be polished on both sides. 
One drawing paper wallet, with lettering paper, file, penholder, 

pens and ink-rag. 
One Linograph (Senior Size) may be substituted for C. D. 

and E. 



1. USE OF INSTRUMENTS. Every article itemized in the 
foregoing list is required and used for a specific purpose. 

2. The uses of the instruments and ways of handling them 
are best explained by demonstrations and proficiency acquired 
by constant practice. 

3. Triangles are used to obtain angles of 15° and 75° as 
shown in Fig. 3. 



TO OBTAIN A^4GLeS, 
?Oo OF 15** AND 15° 
-^sToXwiTH TRIANGLE 
1 





Fig. 3. 



I 



4. Chisel points must be used on all instrument leads and 
pencils. Cut the wood back for IJ", exposing the lead for f", 
then flatten the lead by rubbing opposite sides on a file and bring 
to a knife edge by using a slight rocking motion. This point will 
have the appearance of the ruling pen point, but broader. 

1. A NUMBER CIRCLE is to be placed in the lower left 
corner of each drawing and tracing. Its size, form and location 
are to be as shown in Fig. 4. 

2. The classification number of the drawing is to be placed 
in the central zone of the number circle. 





Fig. 4. 



Fig. 5. 



3. The course number is to be placed in the top segment 
of the number circle and the class section number in the bottom one. 

4. A drawing showing more than one part, each having an 
individual part number, must have the part numbers in separate 
circles. 

5. The part number circle is placed near the principle view 
of the part and connected to the view by a leader as shown in 
Fig. 5. 

6. Pattern numbers are serial numbers entered thus: Patt. 
8765 on the principle view in a conspicuous place. See Fig. 5. 



8 



7. Tracing index number is a serial number assigned, for 
designating and filing purposes, from an index when a tracing is 
completed. Block letters and numbers |" high as shown in Fig. 40 
are suitable for this purpose. The letter designating the size of 
sheet and the serial number are placed on the lower right margin 
as shown in Fig. 8. 

SIZE OF SHEETS. 1. Drawings are to be made on sheets, 
cut and ruled to one of the forms shown in Figs. 6, 7 and 8, as 
specified for each type of work. 

2. Form 1-E signifies a sheet cut exactly 10" x 14" and ruled 
with a I" margin. 

3. Sheets are to be trimmed to size after the drawing has 
been completed. (See reference on trimming.) 

SIZE OF TRACINGS. 1. Tracings are to be ruled and 
trimmed to one of the sizes shown in Fig. 8 unless specific orders 
to the contrarv^ are given. 

2. A tracing is trimmed to size after it has been checked 
and all corrections have been made. (See reference on trimming.) 







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SIZE 




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SIZE 


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B 


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SEE LETTERING Arsio TITLES 

E-1234 



Fig, 



10 

TRIMMING. 1. Trim drawing paper with a sharp penknife, 
using the lower edge of your T square as a guide and the back 
of your drawing board to cut on. Never use the face of board 
or table top. 

2. Trim tracing cloth with shears, leaving I" outside of margin 
all around for thumb tacks, trim tracings to size after they have 
been checked and corrections made. 

3. Drawing and tracing sheets must not be off size, care- 
lessly trimmed or have thumb-tack holes in the margin. 

PROJECTION. 1. Perspective projection gives on one 
plane in one view an image of the object as the eye sees it. The 
image is formed on the plane of projection at the intersection with 
it of projection lines drawn from a point (the eye) to all points 
of the object. This method finds its greatest use in Architecture. 

2. Axoni metric projection gives on one plane one view of an 
object that shows its three dimensional surfaces, length, height 
and width. The method is used to obtain pictorial effect, the 
illustration in Fig. 10 having been drawn by this method. 

3. Isometric projection, a particular type of axonimetric 
projection, is used as a ready means of making a Mechanical or 
Freehand Isometric Drawing of an object. This method was 
used in drawing the illustration for Fig. 9. (See reference on 
Isometric Drawing.) 

4. Orthographic projection gives on one plane as many views 
of an object as may be desired by revolving into that plane all 
planes of projection. A projection (view) on a plane of projection 
is formed on the plane at the intersection with it of parallel lines 
drawn perpendicular to the plane from all points of the object. 
See projection on horizontal plane in Fig. 10. (Read para- 
graph 11.) 

5. Co-ordinate planes of projection are two planes, one 
vertical and one horizontal, intersecting at right angles and form- 
ing four dihedral angles known as first, second, third and fourth 
angle, as indicated in Fig. 9. 

6. A profile plane of projection is one at right angles to the 
two co-ordinate planes; it is shown in Fig. 9. 

7. Auxiliary planes of projection are planes other than the 
co-ordinate and profile planes and when used they must be passed 
at right angles to a previous plane of projection. 

8. All planes of projection are considered indefinite in extent. 
An object may be placed anywhere in any one of the four angles 
and projected upon the planes. 



11 



9. Third angle projection gives the most logical and practical 
views; it is used universally in American practice and all drawings 
are to be made accordingly unless otherwise directed. 

10. In third angle projection the planes of projection are 
between the observer and the object. Let it be assumed, as in 
Fig. 10, that the object is surrounded by transparent planes of 
projection and the object to be projected on all of the planes by 
drawing projection lines as shown on the horizontal plane. 




5 C^/7 /30/7?6>/r/C 



Fig. 9. 

11. Projection lines are lines drawn perpendicular from 
points of the object to the planes of projection. 

12. The trace of a line is a point where the line, prolonged 
if necessary, cuts a plane. 

13. The trace of a plane is a line where the plane, extended 
if necessary, cuts another plane. 

14. The true length of a line or the true size and shape of 
a plane surface will be the projection of the line or surface on a 
plane parallel to the line or surface. 

15. A Descriptive Geometry should be consulted for a 
complete treatment of the subject. 



12 



PROJECTIOKI OR VIEVSA 



GROUND LINE 



COORDINAT 
PLANES 



PROJECTIOlU 
LINES 




POINTS 



TRACES 



Fig. 10. 



PLAN OR 
i-J TOP VIEW 



LEFT SIDE VIEW 



FRONT VIEW 



RI6HT SIDE VIEW 




X 




OR ELEVA 



TIONS 



BACK VIEW 




BOTTOM 
VIEW 



THE ViEWS MARKED THUS X 
ARE THE ONES MOST USED 
IN PRACTICE. THE OTHER 
VIEWS AND THOSE ON 

oblique: planes are used 
when conditions require 

THEM 



Fig. 1 



13 

ARRANGEMENT OF VIEWS. 1. Let one of the planes, 
A B C D, in Fig. 10, coincide with the plane of the paper and revolve 
each of the others about its intersection with that plane and toward 
the observer, until they are all in the plane of the paper, then the 
views will be in their proper relative positions. 

2. The names and positions of the views when properly 
projected and revolved are shown in Fig. 1 1 . 

SCALES. 1. Full-size drawings of objects are not always 
possible or practical, and in such cases they must be made one-half 
size or some other conventional size. A scale is used to make a 
drawing less than full size. 

2. A scale is a fraction of the unit measure, one foot in U. S. 
practice, subdivided into the same number of parts that the unit 
is divided and is used in the same way as the full-size unit. 

3. The standard scales used in Machine Drawing are 9\ 
6\ V, 3'\ 1\ \\" and V to the foot. Drawings should be made 
to one of these scales or full size (never larger). 

4. Scales 3", \\\ f^ \\ f^ \\ A^ i^" and \" to the foot 
are used by Architects. Scales 10, 20, 30, 40, 50, 100 feet to an 
inch are used in Civil Engineering work. 

5. The words size and scale should not occur together. 
Either Half size or Scale 6'' = r is correct. Scale half size is 
incorrect. Scale 9" to V is A, or f size. Scale 3" to 1' is tV, or 
\ size. 

6. To determine the scale for a drawing assume rectangles, 
as in Fig. 12, to represent the least areas which will contain the 
different views desired. The dimensions of the rectangles being 
the overall dimensions of the object to be drawn. If A-fB is less 
than Li, the length of the paper, the drawing can be made full 
size, provided C + D<Wi. If the paper is not large enough, 
multiply the dimensions (Li and Wi) of the paper by 12 divided 
by a scale; that is, either I, 2, 3, 4, 6 or 8, until the paper is 
increased enough to draw the object full size; the reciprocal of 
the multiplier will be the size the object can be drawn on the 
original paper size Li+Wi. If, for example, a sheet should have 
to be made four times longer in order to draw the object full size, 
the object can be drawn \ size, or scale 3" to 1' on the original sheet. 

7. Decide which views are required to properly and clearly 
show the object, before starting the drawing, and lay out the 
sheet so that the views, when properly placed, will leave room for 
the title. Move the views from the center of the paper rather 
than reduce the scale. 



14 



LAYING OUT VIEWS. 1. The distance between views 

(F and J, Fig. 12) should not be less than |" or more than IJ", 
depending on the space required for dimensions. 

The rectangles previously referred to in Fig. 12 are not to be 
used in the actual laying out of the views. 

2. The distance between views and margins is determined 
graphically as follows: Lay off from the left margin a distance, 
to the scale that will be used, equal to the overall lengths (A+B, 
Fig. 12), of the views and add on the full size distance allowed 
between views and measure to full size the remaining distance 




NOTE 

/JLl DRAW/A/6S 
MUST BE MADE 
W/TH THE BASE 
LINE EAC/NG 
THE BOTTOM 

OR RIGHT 
HAND MAR&/N. 
LAY OFF ALL 
CENTER LINES 
AND COHSTRC/a 
F/?OM THEM. 



Fig. 12. 



to the right-hand margin. This remainder is divided equally 
between the two sides (H and K), but is not figured closely. 

3. To lay out a drawing the important center line or base 
line in each view is carefully located and from these the drawing 
is accurately constructed. 

Begin at the left and (see Fig. 12) mark off the full-size 
distance (H) that the view will be from the left margin; add to 
this the scale distance to the center line, and so on to the successive 
center lines. The horizontal center lines are located by measuring 
from the top margin. 



15 

4. Accuracy in laying out a drawing is necessary, since the 
operation of drawing is that of building up on paper the views 
of an object, which in most cases does not exist; in other words, 
it is designing (building) by steps, and inaccuracies in the building 
are not permissible. 

5. Draw the views simultaneously. There is no gain in 
completing one at a time. Observe the principles of projection 
and the practice of reading drawings from the bottom and the 
right margins of the sheet. 

6. The base of an object on the drawing should face the 
bottom or right margin to avoid having the object appear inverted. 

v\5ie>\_E. OR ruL_\_ L_\Nie. 

LIGHT l_lh4E:, RAT^O IT0 3, shade: L-\NE:. 



invisible: or dotteid i_\rNiE:s. 

Br.E:/=\K JOJISiTS Vv'HEir^ LltvlElS> /\F^E1 /\dO/^ CEHsJ- 



CEirNTEiR line:. 



DIMENSION \_INE: 



CONSTRUCTION L\Ne 



IRREIGULAR LINE: 
Fig. 13. 

LINES. 1. All drawings are to be made with a 6H sharp 
chisel-pointed pencil. The pencil work is to be clear and distinct 
and have a finished appearance before any inking is done. It 

is not necessary to pencil cross-hatching or dimensions on a drawing 
that is to be inked. Cross-hatching may be done lightly freehand 
to indicate the areas to be sectioned. 

2. Full lines are drawn for all visible edges. (See Fig. 13 for 
width of line.) 

3. Dotted lines are used to show hidden edges, 
and should be drawn when the clearness of the 
drawing is thereby furthered. (See Fig. 13.) These 
lines are in reality short dashes with spaces about 
i the length of the dash. The first and last dash 
of a dotted line should touch the lines at which 
Fig. 14. the hidden edge actually terminates. (See Fig. 14.) 



THU5_ 
NOT 



16 

4. When parallel dotted lines lie close together, stagger the 
dashes and spaces as shown in Fig. 13. The eye then can more 
readily follow the lines. 

5. The full lines in the two views, Fig. 15, represent lines in 
full view, and the dotted lines hidden ones. If the drawing is too 
much complicated by showing all the hidden edges, some may be 
omitted, provided the clearness of the drawing is not impaired. 




Fig. 15. 



6. Center lines are long dash and dot black lines somewhat 
lighter than the outline. (See Fig. 13.) They are drawn through 
all axes of symmetry, the centers of all holes, bolts and rivets and 
where dimensions are to be given from some fixed line. The break 
should not occur where a line is crossed. (See Fig. 15.) 

7. Center lines may be drawn continuous between different 
views of the same object; they must be offset for clearness when 
views of different objects are adjacent. (See Figs. 15 and 16.) 

8. Irregular lines are used to denote a break when a portion 
of a view is shown in section. (See Figs. 13 and 17.) 



17 



f^Srt 




18 



9. Construction lines (see Fig. 13) are fine dash lines and 
are used largely in elementary work; they connect the projections 
on two adjacent planes. These lines should not touch the points 
between which they are drawn. (See Figs. 9 and 10.) 




Fig. 16. 



10. Adjacent part lines are drawn like construction lines. 
They are used to show a part that is adjacent to the piece drawn. 

11. Extension lines are full light lines used to prolong the 
lines of a drawing in order to place a dimension away from the 
view or at a more readable place; they should not quite touch 
the view so that they may not be taken for part of it. (See 
Figs. 15 and 17.) 



19 

SHADE LINES. 1. To distinguish readily between depressed 
and raised portions of an object, and to make the drawings stand 
out, some of the Hnes are made heavy. The Hght is supposed to 
fall on all views of the object from the upper left-hand corner of 
the drawing, in parallel rays, at an angle of 45° with the plane 
of the paper as shown by the arrows to the left in Fig. 16. The 
division between light and dark surfaces is indicated by a heavy 
line about three times as thick as the outline. No account is taken 
of the shadows cast by one portion of the object upon another. 
In many cases the position of shade lines is entirely conventional; 
for example, in Fig. 15 the lower lines of the right-hand view do 
not, strictly speaking, represent the divisions between a light and 
a dark surface, yet it is the custom to shade them as shown. 

2. Place all shade lines outside the outlines of the figure. 

3. A line common to two surfaces is not shaded when both 
surfaces are visible. 

4. Shade the views independently of each other. By placing 
a 45° triangle on the T square (see Fig. 16) and assuming the 
hypotenuse to be the ray of light, it is easy to determine, by sliding 
the triangle along the T square, on just which surface the light 
does not impinge. (See Fig. 13 for width of line.) 

5. To shade a circle or arc always move the needle point of 
the instrument, without changing the radius, down to the right 
at an angle of 45° and a distance equal to the desired thickness of 
the shade line. Do this by eye. (See Fig. 16.) This will make 
the shade line blend into the outline at the proper place, i. e., where 
the light ray is tangent to the curve. By placing the needle point 
in the original center and springing the pen slightly outward, the 
space between the original and eccentric curve can be filled in easily. 

6. To shade an arc that joins a shade line at each end, change 
the radius without moving the needle from the original center, 
draw a concentric arc and fill in the intervening space. 

7. Pencil lines are not shaded. 

8. Shade lines are not used on tracings. All lines are heavy. 

INKING IN. 1. The majority of beginners make the mis- 
take of drawing very fine ink lines; they look neat but are not 
practical. If the nibs of the pen are forced close together the 
ink will not flow readily and the result is a fine gray line. A fairly 
heavy black line is correct (see Fig. 15); this may be obtained by 
opening the nibs of the pen so that the ink flows freely. 

2. The outside of the pen must be kept free of ink. Never 
allow ink to harden in a pen; wipe frequently, and when through 
using see that the pen is quite clean. Do not scrape with a knife. 



20 



3. When inking a drawing, first draw all circles and arcs, 

shading them as you go; after that draw the Hght straight lines, 
and finally the shaded straight lines. Dotted lines are not 
shaded. 

4. Lines, letters and figures must be black. If they have been 
lightened by erasure go over them until they are black. 

5. The surface of the paper that has been roughened by 
erasures, so that ink will spread, can be restored by rubbing it 
with a piece of hard-surfaced paper, the finger nail, a piece of 
polished bone, ivory or celluloid. 

6. Keep your paper and materials free from dust and particles 
of eraser to avoid blots and errors. Dust the drawing frequently. 

DIMENSIONING. 1. In dimensioning a drawing, full light 
lines are drawn to connect the points between which a dimension 
is to be given. The lines are terminated by arrow heads, and the 
dimension is written in a break, usually but not necessarily in the 



make: FIGUREIS THUS ia3-45GTS90 



1 



1^' 



6?1 



h- 



(a^Fini^hed- 



FiG. 18. 






8 



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center of the line, provided for that purpose, as in Figs. 13 and 17. 
Dimensions should be kept in line. (See Fig. 15 at top and 
Fig.. 18.) 

2. Arrow heads are to be made with a fine writing pen. They 
should be small, neat and sharp, and touch the line to which they 
refer. (See Figs. 18 and 19.) 

3. Figures. — ^All dimension figures on a drawing should be 
as near the same size as possible and not in proportion to the size 
of the dimension or drawing. Figures ^" high, made as shown 
in Fig. 18, are large enough for all practical purposes. 

4. Figures printed in a line with lettering, as in a note or 
title, are made as high as the capital letters. 

5. Figures must not be placed on top of lines. Keep them 
in the open where they can be read distinctly. (See Fig. 19.) 

6. When the space is too small to contain a dimension, the 
arrow heads may be reversed and placed with the dimension 
outside the space as shown in Fig. 19. 



21 



7. For lack of room a dimension or note may be written in 
a convenient place and connected to the required point by a 
straight leader. Such a leader should always have an arrow head 
to indicate the point to which the dimension or note refers. (See 
Fig. 19.) 

8. Fractions must always have the dividing line made thus: 
I", never ^", the figures in the numerator and denominator should, 
for clearness, be ^" high the same as the whole number (see Fig. 18) 
and should not touch the line. 

9. Inch and foot marks should be made neat and distinct 
(see sample under abbreviations) and accompany every dimension. 
(See Figs. 17 and 18.) 

10. Dimensions may be placed directly on the views but 
this frequently crowds the drawing too much. Dimensions should 



€'Dr/// 




SA/otfo^ca/er 

Fig 19. 



— ^/z ^ 



be placed outside the views wherever clearness is gained thereby, 
using extension lines between which the dimensions are given. 
Dimension the views in blank before entering the dimension fig- 
ures; that is, draw all extension lines, dimension lines and arrow 
heads first. Dimensions must be kept in line as shown at the top 
of Fig. 15 and in Figs. 18 and 19. 

11. Dimensions may be placed on a section but not on top 
of cross-hatching. Dimension a drawing before cross-hatching it. 

12. Dimension figures must always be placed at right angles 
to the dimension line and read only from the bottom or right- 
hand side of a drawing. (See Fig. 17.) 

13. Dimensions of machine parts are usually given in inches, 
thus: 2Y , 21 '\ the inch mark being placed after the figure. In 
large work, dimensions over two feet are given in feet and inches, 
thus: 4'~()^ 20'— 8|", 3'— OJ". A dash between feet and inches 
and a zero for no inches are essential to avoid errors, 



22 

14. All necessary dimensions must be placed on a drawing 
and care taken to avoid repetition. Give dimensions from finished 
surfaces wherever possible, from center lines, and from one center 
line to another. Center lines must never be used as dimension 
lines. 

15. The size and location of holes must be given on the 
circular view. Locate holes from center lines or from center to 
center. Give cord distances and pitch circle diameter for holes 
on an arc; angular distances are undesirable. 

16. Give dimensions to full lines, in preference to dotted ones, 
wherever practical. 

17. Useful dimensions are those which are of most service to 
the user of the drawing who should never be required to do any- 
calculating. A little thought as to the process the material must 
undergo in the construction of the object, will quickly determine 
what dimensions to give. 

18. Over-all dimensions are useful in getting out material 
and should be given where needed. 

19. Distribute the dimensions among all the views and do 
not crowd too many into one. Select dimensions that are the 
best for each view. 

20. A circular arc is dimensioned by a radial line, which need 
not extend to the center, with an arrow head only at the arc as 
shown at the fillet and round comer in Fig. 15. 

21. Circular pieces and bores are dimensioned by diameters, 
whether the complete circle or only a part of it is drawn; in the 
latter case Diam must be printed after the dimension figure and 
the dimension line extended beyond the center as shown in the 
semicircular view, Fig. 3S. 

22. Distances not to scale, as on a foreshortened view of a 
structural or other long piece, must have Not to Scale printed after 
the dimension figure. (See Fig. 19.) 

OMITTED DIMENSIONS. To determine if a dimension 
is missing, scan for arrow heads the line, in all views, to which 
a dimension is desired. If no arrow head touches the line, that 
dimension is missing. 

TABULATED DIMENSIONS. 1. Parts that are similar in 
shape but different in size should have only one of the parts drawn 
and the dimensions of all parts tabulated as shown in Plate I. 
Dimensions that are common to all of the parts may remain on 
the^views. 



23 

ABBREVIATIONS. The abbreviations and symbols most 
commonly used in practice are shown in Fig. 20. 



Anol£ L 

G^/vr/^/F TO ar/vrr/f ^ybi^ 

C//FC6/IA/? /=^/rc// CJ? 
C/f^cuMre/^^A/ce C/rcam. 

D/AMET/^AL ^/rcU D. /? 

O/AMET^/P Diarrr. 

F^-eT rt or ' 

F/A//SH MARK h 



/■/S^AGONAL H^X. 



LeFTHANO 
0(/T3/0£' 



//?s. or 

as. 



P/TCH C/RCl£ D/AM, PCP^ 

ffA D/us ^ac/.or /? 

f?/GHTHAA/0 /?// 

Square Sc7. 

7nr£aos T/jc/s. 



Fig. 20. 



FINISH MARKS. Finish marks indicate that the surfaces 
marked must be machined to the exact dimension given, not 

necessarily polished. They are made with a writing pen (see 
Fig. 21) and should read from the bottom of the drawing only. 
(See Fig. 17.) The casting or forging is made full, where indicated 
by a finish mark, to allow for machining. When a piece is to be 
finished all over, omit these marks and print "finished" in the 
general title. (See Titles.) 



/VAZ/SH MARKS ^ SHOULD ALWAYS BE LARGE AND D/ST/NCT 




%^^=^ 



W ,1^ ^"^ 



^M^ 



Fig. 21. 



24 



FINISHED SURFACES. The mechanical operations that 
are required to finish a surface are Boring, Broaching, Chipping, 
DrilHng, FiHng, IMilHng, Planing, Reaming, Scraping, Shaping 
and Turning. 

The operation may be specified on the drawing for any given 
surface as a guide to the artisan. 

FITTING SYMBOLS. Parts that fit together, as a wheel on 

a shaft and a shaft in a bearing, must have an allowance made 
for tight or loose fitting of the parts. Conventional Fitting Sym- 
bols and their uses are shown in Fig. 11. 



FfrrrmSYMBOL^ XX ^^^^^Z^Jf:^ 

EASY DRIVE- ^/7C^t 

3UCK/NG r/T- S/7c?/9 

5L/D/NG <S F?UNN/N(5F/T 
S/?c9/t/ess thdfn /po/<s . 
) CLEARANCE- /Vot 

F'OL/SH— A/o exc?iat 

3/ze,. 
SC/f^F'E — To // / O^ 

RF ^ouG/y /=y/v/S/^~ A/a 

G &/=f/ND - 

Fig. 22. 




SECTIONS. 1. As the object of a drawing is to represent 
the exact construction of the machine or part drawn, it is often 
convenient for clearness to draw some of the views or parts of 
them as sections through the object. Thus, in Fig. 17, the upper 
half of the right-hand view represents a secvion on a plane A — B 
that is normal to the vertical plane of projection. That is, 
we assume the near portion of the upper half of the object (as 
shown in the right-hand view only) to be cut away, back to the 
section plane, showing the construction of the object as it appears 
at that section. 

2. The trace of a section plane must be lettered, in one of 
the views, and a note placed directly under the view stating where 
the section is taken; thus, Section on A — B, Section on X — Y — Z. 
Inclined lower case letters are used for this notation. (See Fig. 17.) 



25 



3. A section plane may be offset, as shown at A — B — C — D 
in Fig. 23, to include portions of an object that are not in a straight 
line. 

4. When the surface of a section stops at a plane through 
the center line, the center line is made a full line as fa4 as the 
section extends, and shaded if the conditions require it. 

5. When the surface of a section extends a little beyond the 
center line an irregular line (Fig. 13) is drawn to show a fractured 
surface. The latter method is frequently necessary to more 
clearly show the detail of the interior; for example, the key and 
keyway in the illustration, Fig. 17. 

A 







T 



n 
t 



xV^ 



-T 




5ectior?onA-B-C-D 




^ecf/or? o/yF'F 




Sect /on ony- Y 



Fig. 23. 



CROSS-HATCHING. 1. All portions of the object cut by 
a section plane are cross-hatched by lines making an angle of 
45°, except where otherwise shown in the "Conventional Standard 
Cross-hatchings" Plate A. Cross-hatching is done after a drawing 
is fully dimensioned, omitting it where the dimension is placed. 

2. All sections of the same piece, in the same plane, are cross- 
hatched in the same direction. Cross-hatching lines are never 
drawn across a full line. 

3. When two or more pieces, of the same or different 
material, show in a section adjacent to each other, the cross- 
hatching must be drawn in opposite directions. (See Figs. 17 
^nd 44.) 



26 



CONVENTIONAL 
STANDARD CROSS -HATCHINGS 





ALUMINUM 




LEATHER 



^ 


-_ 


-^ 




,__ .. 



WOOD 



^m^ 



RED BRICK 





CAST IRON WROUGHT IRON MALLEABLE IRON 




WROUGHT STEEL 



yY^TTv 



:>7i;^^' 






BRONZE 






BEARING METAL 




A5BEST05 



LIQUID 



V/M / ////////A 



y/////////y////. 



Y//A'/////////A 



FIRE BRICK 

Plate A. 




TOOL STEEL 




VULCANITE 




WIRES 




GLASS 



m 



2£ 



wznM. 




a^—ZW^ 



3 



^ 



^^ 



STONE 



27 

4. Care should be taken to space the cross-hatching uniformly. 

This is readily done by eye, after a little practice on a separate 
sheet of paper. The appearance of a drawing, which is otherwise 
faultless, is often spoiled by poor cross-hatching. 

5. Cross-hatching lines should be somewhat finer than the 
outline and not too close. Use about a ^" space. They may be 
drawn across center lines. 

6. The system of conventional standard cross-hatchings to be 
used in sectioning is shown on Plate A. Note the spacing and 
width of line. 





HAFT 



BAR 





WOOD 



PIPE 




T 



^M3l_E IROrsI 



teie: iron 



] 



I 



CHANNEL. IRON I BEIAM 

Fig. 24. 



7. Axles, Balls, Bolts, Cotters, Keys, Shafts, Spokes of 
Wheels, Valve Stems, etc., are not cross-hatched when a section 
is taken longitudinally through them, but are drawn full as though 
the cutting plane did not pass through them in order to make a 
drawing clearer. (See Figs. 17 and 23.) 

8. Ribs, Webs and similar thin parts are not cross-hatched 
when a section is taken lengthwise through them. An alternative 
method used to some extent shows every other section line drawn 
across the rib or web. (See Fig. 23 for both methods.) 



28 

9. A shaft, bar, or other long piece that cannot be shown 
in its full length to a practical scale is represented broken as shown 
in Fig. 24, the break showing roughly the outline of the cross- 
section of the piece. 

10. Long structural details are always drawn foreshortened 
(other pieces may be if advisable) without a break showing and 
the dimension marked Not to Scale. (See Structural Drawing 
Details.) 

TINTING. 1. When a large area of a drawing on paper or 
cloth is in section it is often more convenient to color the section 
than to cross-hatch it. This method is used in Architectural and 
Civil Engineering practice. 

2. A drawing should be fully inked in with water-proof ink, 
freed from pencil marks and well cleaned before the color is applied, 
as the color is readily removed with a pencil eraser. A cleaning 
rubber will tone it down if too dark. 

3. A section on paper or the dull side of tracing cloth may 
be colored by rubbing a soft black lead pencil over it. For pro- 
ducing distinctive colors the ordinary colored crayon may be 
applied generously and then blended to a uniform tint by rubbing 
the surface with a piece of cloth dipped, in gasoline. Any color 
outside of the section is readily erased with an art gum eraser. 

4. Colored inks, standardized, and moist water colors are 
also used for tinting sections. These liquid colors may be used 
sparingly on the dull side of tracing cloth. The cloth will wrinkle 
if too moist. 

5. For tinting sections with moist water colors use the ones 
named for the materials given in the list below. 

The color mentioned first, for a given material, should pre- 
dominate in mixing the tint representing that material. In any 
case, a very small quantity of color will suffice. 

Cast Iron Paynes Gray. 

Wrought Iron. . . .Prussian Blue. 

Wrought Steel . . . Prussian Blue and Crimson Lake. 

Cast Steel Crimson Lake and Prussian Blue. 

Brass Gamboge. 

Bronze Gamboge and Crimson Lake. 

Copper Crimson Lake and Gamboge. 

Babbitt Water thinned India Ink. 

Leather . .Water thinned India Ink and Burnt Sienna. 

Wood Burnt Sienna. 

Glass Prussian Blue and Gamboge. 



29 

6. Go over the portions to be tinted with a brush, using 
clear water, just before applying the tint; this will prevent the 
tint from drying too rapidly. Make the tint light, then, by going 
over it again, if necessary, the proper shade may be obtained. 
Mix the tint in a saucer and stir with every dipping of the brush. 
Remember that the process is that of tinting and not painting. 

7. A smooth tint will result if it is done quickly, working 
from left to right and downward. Keep a drop of tint on the 
paper just ahead of the brush and leave the part tinted practically 
dry. An excess of moisture remaining will cause the tint to dry 
blotchy. If the tint runs over a line, brush back quickly with 
the finger. 

8. When the area to be tinted is quite large, the paper should 
be stretched. This is done by thoroughly wetting the entire 
paper and pasting it, along the edges, to the drawing board, allowing 
it to become thoroughly dry before starting the drawing. 

9. Lines and dimensions may be placed directly on any tinted 
surface if necessary, but cannot be erased without removing the 
tint. 

LINE SHADING. 1. Line shading is used to represent more 
clearly or more quickly the contour of the surfaces of which the 
piece is composed. 

2. This method is used where the number of views is limited 

or where it is desired to represent to those who are not familiar 
with the principles of mechanical drawing, the construction of a 
machine or some part it is desired to emphasize. 

3. Book and magazine illustrations and Patent Office draw- 
ings are examples in the use of line shading. 

4. The distribution of light and shada found in current practice 
in the case of a circular cylinder can be produced by assuming the 
illumination to come from the opposite sources S and Si (Fig. 25) 
in parallel rays, their vertical projections making 45° with the 
horizontal plane of projection and their horizontal projections 
at 45° with the ground line. Source S is to the left and back of the 
observer. 



30 



LINE SHADING 



D , 



^ 



I 




Fig. 25. 



31 

5. The brightest part of an illuminated object is that which 
reflects the rays of Hght directly into the eye of the observer. 
Assuming the Hght to fall as above described, and knowing the 
angle of reflection R must equal the angle of incidence I, reference 
to Fig. 25 will show that the high light element must be 22 J ° 
around from the center line C L. At this element only, the rays 
of light would be reflected normal to the plane of projection and to 
the eye of the observer. 

6. The dark element, or no light, is 45° around on the opposite 
side of the center line C L, for at this point the light rays are 
tangent and there is no reflected light. Beyond this element 
the surface is slightly illuminated by the rays Si coming from 
below upwards as assumed. 

7. The limiting elements A B and D E (Fig. 25) are of the 
same shade. The shades received by all surfaces of revolution are 
shown by lines which represent the generatrix in various positions, 
the intensity of the shade being effected by the thickness of the lines. 

8. First, ink the outline of the drawing with a uniform line; 
omit dimensions, dotted lines, shade lines and center lines, 
although the latter are always penciled for construction. Second, 
ink the shading, the straight lines first, and then the curved ones. 
Avoid making lines fine or too close together. 

9. Practice line shading different surfaces on a separate 
sheet of paper before line shading a drawing. 

10. Examples of line shading will be found on Plates B, C, 
and D, which cover most shapes met with. Study them and 
apply to your special case. 

11. Do not use a knife on line shading; use a rubber to erase 
errors, then restore the surface of the paper by rubbing it with 
another piece of paper. 



32 




Plate B. 



33 







■^t Fi ^^c/ X to he founaf /?/ tr/a/ 



Screw threads t/?(7/'c7re^ or over //? c//c7/77efer; ^Ae/? 
c/rc7\A/r? to 3ca/e. 5/70(//c/ he a^rai^/7 to the exact sha/?e 
c//^c/ p/tc/?^ //?e Ci/r\/e of t/?e /?e//x /?e//?y r?ey/ecrec/, 
^/7t:/ 3haafe as show/? c?t A ar?afB . l4^/7e/7 L//7aer ^ D/h/?7. 
use The co/yver/f/o/ya/r^ethoc/s Ec?/7(^ f 



Plate C 



34 




- C-DlltoA-B 

Prolong straight 

lines to meet A' B 

With radii X-A'C 

(7/7^^ o/7iy'Dc/rav\/ 

the arc6. 




Drc;^wA-Can^A-B DrawC~D //toA-B. Dra^C-E 
± toE~H, DrawE'B. Pro/ony stra/y/jf //he 3 to 
ES. W/fh rac/// X'^CE (7/7^ po/7 C-Dc/raw the area. 



Plate D. 



35 




f 



-Y 



B 






^i^^WXWW^ 



M 



8 lO^ 



5 
8^ 



^/(^n of /Vo/e 



^m^^ 



I. 



sV 




T-N 



^/Yo/e 



iph ^: 



Fig. 26. 



INTERSECTIONS. 1. The intersections of curved surfaces 
should be drawn as an aid to the understanding of a drawing. 
The Hne of intersection of two pieces must be carefully plotted 
when it is required that one or both pieces be cut to fit together 
at the line of intersection. (See Developments.) 

2. Descriptive Geometry treats of the methods employed in 
finding intersections, but the student unfamiHar with this subject 
can plot most of the simpler ones met with in practice if he observes 
the following instructions. 



36 




« 



Fig. 27. 

3. To determine a point on the line of intersection of two 
surfaces, pass a plane through both in a way that its trace on 
each surface will be an element or other known line, these elements 
will intersect at a point on the line of intersection of the surfaces. 

4. A sufficient number of points should be plotted to deter- 
mine the shape of a curve of intersection. Approximate the 
curve by drawing a light freehand line through the points plotted, 
as a guide for applying the Irregular (French) Curve. With the 
aid of the Irregular Curve a smooth curving Hne is drawn through 
the points. 

5. Two intersecting cylinders, A and B, with axes at right 
angles and in the same plane are shown in Fig. 26. I is their 
line of intersection, its shape being determined by plotting points. 



37 

These points are the intersections of elements in the cylindrical 
surface A with elements in the cylindrical surface B. Element 1 
of A intersects element 1 of B at F and element 3 of A intersects 
it at 3"". Element 2 of A (see end view) intersects element 2 of 
B at 2^; this point projected on the vertical plane is V , and is the 
lowest point of the curve of intersection I. Intermediate points 
such as 5^ are found by passing planes in such a way that they cut 
elements from each cylinder, the intersection of the elements in 
any one plane being a point on the curve. For example, the plane 
X — Y at any distance S from the center line (see end view) cuts 
element 4^5^ from A and 6^5^ (see top view) from B. The points 
5^ and 5^ projected on the vertical plane determine 5^. This 
point, being the intersection of two elements, is a point on the 
curve of intersection. Another point, T , is determined by 
projection from 7^. \^ 

6. Cylinder B (Fig. 26) is hollow and has been broken away 
to show a hole cut through its lower portion. This case is similar 
to the previous one, the difference being that the thickness of 
the cylinder is shown and the surface of the hole therefore inter- 
sects the inside as well as the outside surface of the cylinder B. 

7. The plane M — N (see end view) contains elements of the 
cylindrical surfaces that pass through the points 8^ and 9^ as well 
as the element of 8^9^ of the semi-cylindrical surface of the hole. 
These are the points in which the elements meet and, if projected 
on the vertical plane, determine 8^ and 9^, which are points on 
the lines of intersections J and Ji. 

8. A pipe elbow with its center at O, intersected by an 
offset cylindrical utlet, is shown in Fig. 27. In this case points 
in the line of intersection I are found by passing planes containing 
elements of the cylindrical surface and arcs on the surface of the 
elbow. Element 2 appears to intersect the elbow at b^, end view, 
but a plane passed through 2 cuts from the elbow, front view, 
the arc b^2''c^. This arc is found by projecting the point b^ to b^ 
on the center line through O, thus determining a point in the plane 
through which to draw an arc with O as its center. The element 2 
lies in the plane of this arc and intersects it at T , which is a point 
on the line of intersection VW . The point T projected to the 
end view determines 2^, a point on the intersection that appears 
in that view. Pass any other plane, as X — Y, at any distance 
S from the center line. The points of the lines of intersection 
that He in this plane are 4"" and S'' in the front view and 4^ and 5^ 
in the end view. A sufficient number of points are to be founcj 
through which curves of intersection may be ch'awn. 



38 



9. Note that between 6'' and V, front view, the Hne of inter- 
section replaces a portion of the arc of the elbow in this view. 
This is due to a portion of the cylindrical piece, 6^8^ 7^ top view, 
5P3P7P gj^(j view, overlapping the center of the elbow. 

10. A bell-shaped surface of revolution (B) intersected by a 
plane surface (S) and a cylindrical surface (C) is shown in Fig. 28. 
(Heavy lines given light ones to be found.) Any cutting plane, 
as X — X, passed perpendicular to the axis of revolution will cut a 
arc of radius or2^ on the surface of revolution and a straight line 




Fig. 28. 



element 2^2^ on the plane surface; this arc and element lie in the 
same plane and intersect at points 2^ and 2^ (projected from 2^) 
which are points on the line of intersection of the two surfaces 
(B and S). 1^ and 3^ are the limit points of this line and its shape 
on the profile plane will be given by the points P, 2^, 3^ found by 
projection. Any cutting plane, as Y — Y, cuts an arc of radius 
ore^ on the bell surface and elements at 6^ and 6^ (side view) on the 
cylindrical surface, also an element at 4^ on the plane surface. 
Project 4^ from 4^ and 6^ from 6^. The elements 6^4^ and 4^4^ lie 
in the same plane and interect at 4^, which is a point on th§ line 



39 



of intersection of the cylindrical surface (C) and plane surface (S) ; 
3^, 5^ and 3^ are the limit points of this line. The element 6^4'' 
and arc of radius ore^ lie in the same plane and intersect at 6^, 
which is a point on the line of intersection of the bell surface (B) 
and the cylindrical surface (C) ; 3^, 7^ and 3^ are the limit points 
of this line and its shape on the vertical projection will be given 
by the points 3^, 6^, V found by projection. Read paragraph 4. 




J\ 



O/oe.'^Jnc} 



ft 6HJ K L 



\i 






/ 



De\/e/op/?7e/7t of 
the upper ha^/f of 
the 3(^uc?re por//or?. 



Deve/op/T^e/^rofthe e///)o//ca/por//i^^. 

YiQ. 29. 



DEVELOPMENTS. 1. The development of surfaces is 
necessary when sheet material is required to be cut to fit together. 

The line of intersection of the surfaces must first be determined 
and from it the development plotted. 

2. An elliptical shaped piece intersecting one of square sec- 
tion is shown in Fig. 29. In this case an auxiliary view A is 
required to show the true size and shape of the elliptical piece. 
The line of intersection F, V , 3"", 4"", etc., was determined by planes, 
as X — X, passed parallel to the axis of the oval piece. These gave 
elements as 6-6^ intersecting elements as H-6, 



40 



3. To plot the development of the elliptical piece draw a base 
line 1, 2, 3, 4, . . . . 13, . . . / . 1 and make 1, 2 equal to 1^ 2^ 
measured on the arc by stepping off carefully with a bow spacer, 
make 2, 3=2^, 3^, etc. Draw the elements 1, 1^ 2, V, etc., 
perpendicular to the base line and equal in length to the corre- 
sponding element on the vertical projection. A smooth curve 
drawn through the points F, V , 3"", etc., plotted on the developed 
surface of the elliptical piece will give the shape the piece must 
be cut to fit the hole in the square piece; this hole to be plotted 
in a similar manner. 




ORTHOGRAPHIC PROJECTION 

Fig. 30. 



i y 3 

/ ,03 

/SB 7 



Fig. 31, 



ISOMETRIC DRAWING. 1. An Isometric Projection of a 

cube is one in which all lines of the cube are of equal length, (isos, 
equal + metron, measure). 

2. Orthographic Projections, 3d angle, of a cube in three posi- 
tions are shown: first, in Fig. 30, with all faces parallel to the 
planes of projection; second, in Fig. 31, rotated through 45° about 
a vertical axis O2; third, in Fig. 32, rotated about a horizontal axis 
O3 until its diagonal (1-7) is perpendicular to the vertical plane. 
The vertical projection of the cube in this position is an isometric 
projection, since all edges of the cube are equal in length. The 
edges are shorter than the true length on the cube. 

3. Isometric Planes are the three dimension planes of the 
cube visible in its isometric projection. (See Fig. ZZ^ 



41 



Isometric Axes are the lines of intersection of the isometric 
planes and are at 120° with each other. (See Fig. 33.) 

4. Isometric Lines are lines that are perpendicular to either 
isometric plane H, V or P, Fig. 33; they are measured in their 
true length parallel to the axes. Non-Isometric Lines must be 
plotted by the Orthographic Co-ordinates of points in the lines. 

5. Isometric Projections of Circles that are parallel to the 
Isometric Planes will be elHpses. The lengths of the major and 
minor axes are not known, as they are in the ellipse which is the 
oblique projection of a cylinder or cone (see Geometric Drawing, 
Plate V, for these.) 



120 




ISOMETRIC PROJECTION 

Fig. 32. 



ISOMETRIC 
AXES >^»^^ PLANES 

Fig. 33. 



6. A circle inscribed in the face of a cube will touch at the 
four diameter points D (Fig. 35). Any points in the circle, as A, B, 
E, M, N, can be projected on an Isometric Plane by laying off the 
co-ordinate distances for each point parallel to the Isometric Axes 
of the circle plane, as X — A and Y — A for point A in Fig. 34. If 
the circle had a dip in it at B to B' perpendicular to its plane and 
then slanted up to E (a situation impossible to show in the one 
view of Fig. 35) the point B' would have to be determined by a 
third dimension, as B — B', Fig. 34, layed off downward parallel to 
the vertical axis. The slant line will be the one drawn from B' to E. 
B — B' is an Isometric Line and B' — E a Non-Isometric Line plotted 
by the Orthographic Co-ordinates of its points. It should be 



42 



noted that the four 45° points F, of the circle, always fall on the 
major and minor axes of the elHpse. 

7. To draw the Isometric of a circle plot its center on the 
drawing and draw through it the two diameter lines D — D parallel 
to the isometric axes in the plane of the circle. Draw lines through 




APPROXIMATE "^^^^ 3 POINT METHOD 

METHOD L. NEARLY ACCURATE 

METHOD5 OF DRAWING I50METRIC PROJECTIOK/op CIRCLES 

SEE GEOMETRIC DR.AW1NG FOR METHODS OF DRA.WING TRUE I 
AND APPROXIMATE E.LUP5ES IF THE LEr4GTH5 OF AXES ARE OIVENJ 

Fig. 34. 



the diameter points D parallel to the diameter lines, a line through 
their intersections L and L will determine the direction of the 
major axis of tl\e ellipse and one through S and S the direction of 
the minor axis. The ellipse may be drawn by one of the three 
methods shown in Fig. 34, the three point method, being easiest, is 
preferred. The arcs in this method are drawn in the order of the 
radii Rj, R2, R3. 



43 




/50METRIC PROJECT\ON 
OF A CIRCL.E 

D 




RAP\0 3 PO\NT METHOD 
Fig. 36. 



8. The Isometric three-point ellipse may be constructed quickly 
by drawing lightly, with C as the center, a circle whose diameter 
D — D is equal to the circle to be projected. The four diameter 
points D and the two S points will fall on this circle and, as shown 
in Fig. 36, they can be readily located with a triangle and are the 
points required to construct the ellipse. 

9. An Isometric Drawing of a portion of a drawer is shown 
in Fig. 37. This illustrates the application of the isometric circle 
in each of the planes and the method of centering a drawing. 




THE UNt B-C-D-E IS 
USED ONUV FDR L AVIN& OU 



^\an isometric 
j^ draw/ins 

/^showing the. 

^/construction 
oi>-a drana/er 

AtMD 
THE METHOD OF 
DIMENSIONING AN 
ISOMETRIC DRAWING. 

THE LINE <t 15 A CENTER LINE 
OF SOLID . THE LINE A-O-C-O-E 
IS A CENTER LINE OF SURFACE. 



Fig. 37. 



44 

SKETCHING. 1. For Freehand Machine Sketching the 
following materials are required: 

Sketching outfit; 

1— Sketch board, U" x 9" x i'^ fibre. 
1— Steel clip, 2i" Bull Dog type. 
1 — Pad cross-section paper, -^^ x j\" ruling. 
1 — 2H lead pencil, Van Dyke or Venus drawing. 
1 — Pencil eraser, E. Faber No. Ill Emerald. 
1—2 ft. rule, Stanley No. 59. 

1 — Pair 6" firm joint inside calipers, B. & S. or other good 
grade. 

2. The tools enumerated above are the only ones to be used 
in making freehand sketches. 

3. The object of a sketch is to give, in as few views as are 
necessary, sufficient information as to the shape and size of the 
machine or the part represented to enable a draftsman to make 
complete working drawings. Sketches are made freehand on 
cross-section paper, unruled paper is used when the sketcher is 
an adept. 

4. Each sketch sheet must contain the name of the machine 
at the top and directly under the views the name of the piece, 
quantity required, material, finish, and the part number. (See 
Fig. 38.) 

5. The sketcher's name, date sketch was completed and total 
time consumed in sketching all views of each piece are to be placed 
as shown on Figs. 3S and 39. 

6. The size of the sketch need not be in proportion to the 
size of the object, but should be large enough to contain all dimen- 
sions without being crowded. When the piece is large or compli- 
cated, each view should be placed on a separate sheet. 

7. If more than one sheet is required, to properly portray the 
piece, page the sheets in the lower left corner as shown in Fig. 38. 

8. The piece should first be sketched by eye, endeavoring to 
maintain its relative proportions before taking any measure- 
ments. 

9. The dimension lines with arrow heads are then placed 
where the dimension figures will show to the best advantage. 
Finally the piece is measured and the dimensions placed in the 
spaces previously provided. 

10. In general, the same views, sections, etc., which would 
be used in making working drawings are used in sketching, except 
that in sketching many abbreviations are used to simplify the 



45 



work. For example, in Fig. 39 only one view of each detail is 
shown, the plan being omitted, and the abbreviations Diam. and 
Hex. added after the dimensions to indicate that those portions 



3^S 



o 



o 



UNIVERSITY OF PENNSYLVANIA ^^^^^<^^^ 

MECHANICAL AND ELECTRICAL ENGINEERING. 




Fig. 38. 



are round and hexagonal. In the same way Sq. for square, Oct. 
for octagonal, and other abbreviations are used. (See Abbre- 
viations, Fig. 20.) 



46 

11. When a piece is symmetrical about an axis, a view of 
one-half of it is sufficient. (See Fig. 3S.) By taking advantage 
of these and similar points, both time and labor are saved. 

12. Parts are to be sketched separately, not assembled. 

13. In sketching large pieces one view may extend over two 
or more sheets of the sketch paper. The portion of the view 
on each sheet must end at a center line or other fixed line on the 
object. 

14. Directions given for dimensioning drawings are appli- 
cable to sketches, although it is better to give too many dimen- 
sions than too few, as one does not always have access to the object 
when he makes the working drawings from the sketches. 

15. Rough castings should be measured to the nearest six- 
teenth and allowance made for draft, when this affects the required 
measurement. 

16. Judgment should be exercised when making measure- 
ments, especially of rough work, as an apparently odd dimension 
may be due to the irregularities of casting or forging. On finished 
work, measure as closely as possible. 

17. Dimensions should be referred to center lines and to 
finished surfaces rather than to rough ones. 

18. The radii of all curves should be given. To ascertain 
these, take a piece of paper and with a pencil mark the outline of 
the curve upon it, and then with a pair of calipers, used as dividers, 
obtain the correct radius. When this cannot be done, take a wire 
or thin strip of lead and bend it around the curve, and with the 
aid of this mark the outline on paper and proceed as before. 
Irregular curves and non-circular arcs should have their ordi- 
nates and abscissas given for use in plotting the curves on a 
drawing. 

19. Holes should always be located by their centers. Where 
there are several holes of the same size, similarly located in a piece, 
it is not necessary to give the diameter of more than one of them. 
When measuring the depth of drilled holes, give the distance to 
the point where they begin to taper. (See H on Fig. 45.) 

20. Tapering and tapped holes should always be noted. The 
number of threads will be understood to be standard unless other- 
wise noted. 

21. To dimension a cavity from which the open caKpers 
can not be extracted, scratch a cross on each leg of the caliper 
and, measuring the distance between their centers, extract the 
calipers and adjust the crosses to this same distance. The meas- 
urement across the caliper points is the one desired. 



I 



47 



^UNIVERSITY OF PENNSYLVANIA Na/T^e/yere 

MECHANICAL AND ELECTRICAL ENGINEERING. 




Fig. 39. 



48 



ho/zhec/ FREEHAND LETTERING Gofh/csfy/e 
L o\A/er crofse /effers^ Numera/s crno/ C^c^/os~ 
Sh/^t Is y/nZ^, Nu/ryer^h with letters crre CAP high 




Plate E. 



49 



LETTERING. 1. Special attention should 
be given to lettering, as, when well executed, 
it adds greatly to the working value of a draw- 
ing. With care and constant practice one can 
do satisfactory lettering. 

2. Bold single-stroke letters are desirable. 
They are easily made, look well and are appro- 
priate on mechanical drawings. 

3. The lettering on all drawings, unless 
otherwise directed, is to be done according to 
the system described in Reinhardt's ''Free- 
hand Lettering," (see Plate E) using incHned 
and upright letters of the "Gothic" type in 
the three heights shown on Plate F. 

4. For the small lettering in descriptive 
matter, notes, dimensions and arrow heads 
a "Gillott No. 390" pen should be used. 

5. For the main title, large letters and 
when filling in, a "Hewitt's Patent Ball Pointed 
Pen," No. 516 F, is most suitable. 

6. Notes and descriptive matter should 
read from the Lower or Right-hand edge of 
a drawing and not in a diagonal direction. 

7. Index numbers on tracings are to be 
made as shown in Fig. 40. 

8. Ruled letters and figures are shown in 
Fig. 41. 



IT I'^TV* 



'/ / /// //^////A(jf? mm 



^ 



/////(// > V/ / ///// 7^. 



^ 



]A/ai:7>^/ .' ^ ^wmmw; 



>m'," /, >/ ,', '/,'/mf /mm 



Fig. 41, 



Fig. 40, 



50 




51 ' • 

TITLES. 1. Every drawing should have a general title 

(see Plate G) containing the following essential information : 

NAME OF THE PIECE. 
NAME OF THE MACHINE OF WHICH IT IS A PART. 

QUANTITY REQUIRED, MATERIAL, FINISH. 

SCALE, NAME OF DRAFTSMAN, DATE COMPLETED. 

TRACED (NAME) CHECKED (NAME) 

APPROVED (NAME) DATE (NUMERALS) 

2. Any one piece of a machine is a detail of that machine, 

strictly speaking, but should not be designated as such in the title. 

Name it in the title when no other parts are drawn. When several 

pieces of a machine are drawn separately on a sheet, it then becomes 

a detail drawing and should have a general title as follows : 

DETAILS OF 

NAME OF THE MACHINE OF WHICH THEY ARE PARTS. 

SCALES. NAME OF DRAFTSMAN. DATE COMPLETED. 

TRACED (NAME) CHECKED (NAME) 

APPROVED (NAME) DATE (NUMERALS) 

3. Part numbers are frequently used as a substitute for names 
of pieces on a detail sheet. These numbers are necessary when 
the pieces are difficult to name concisely or are numerous and 
similar. '' Part number — " replaces " name of piece " in the 
sub-captions. On the assembly drawing the numbers must appear 
in circles with leaders to the parts designated. (See Fig. 5.) 

4. The Location of the Title on Drawings is shown on Forms 2, 
3 and 4, under size of sheets, and on Plates G, J and K. 

Note the varying heights of each line of words according to 
their importance, also the symmetrical appearance of the titles. 

SUB-CAPTIONS. 1. A sub-caption is to be placed under 

each piece on a detail sheet (see Plate G); it should contain 

the following essentials: 

NAME OF PIECE. 

QUANTITY REQUIRED, MATERIAL, FINISH. 

SCALE. 

2. If the scale is the same for all the details it should be 
omitted from the sub-caption. Avoid using more than three 
scales on the one detail sheet. 

A BILL OF MATERIALS should be placed on drawings 

that show several pieces assembled. Its form should be as shown 

on Plate H or J and should contain the following essentials: 

BILL OF MATERIALS. 

PRINCIPAL PIECE, QUANTITY REQUIRED, MATERIAL, FINISH. 

SECONDARY PIECE, QUANTITY REQUIRED, MATERIAL, FINISH. 

SMALLEST PIECE, QUANTITY REQUIRED, MATERIAL, FINISH. 

The " Quantity required " in the title would be the number 
of units wanted. A unit being an assemblage of all the pieces 
specified in the bill of material. 

The words '' as shown " should be substituted for " material " 
and " finish " in the title when a bill is given. 



52 



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57 

ASSEMBLY DRAWINGS. 1. When a portion or the whole 
of a machine is drawn showing the various parts joined together 
in their relative positions, it is known as an assembly drawing. 

2. In laying out the drawing of a machine, the designer must 
make the assembly drawing first, the details being drawn out to 
larger scales afterwards. On assembly drawings it is often well 
to show sections on different parallel planes in the same view. 

ERECTING DRAWINGS. 1. Erecting drawings are those 
which show all the parts of the machine in place, but neglect the 
unnecessary and minute details of construction. They are fre- 
quently drawn to a scale smaller than that of the original design 
and are sent with a machine to be used in setting it up at its 
destination. 

2. Erecting Drawings should have sufficient dimensions to 
enable the erectors to distinguish and place the various parts in 
their proper relation to each other. 

TRACINGS. 1. For reproducing drawings, without injury to 
the original, tracings of them are made upon tracing paper or cloth. 

2. Tracing cloth or linen is used almost exclusively, owing to 
its wearing qualities. It is a specially sized and calendered fabric, 
having one side glazed and the other rough, the former being 
known as the smooth side, the latter the dull side. Tracings can 
be made on either side of the cloth, but the side used should be 
thoroughly rubbed with powdered chalk or soapstone to remove 
greasiness and permit the ink to "take" more readily, the excess 
chalk must be thoroughly cleaned off before starting to trace. 
Tracings partly inked may be rubbed with powder, if the ink 
fails to take, without injury to the lines. 

3. The dull side of the cloth is to be used for all tracings 
unless otherwise directed. It is easier to draw pencil lines on the 
dull side when making additions to views or checker's corrections. 
Drawings traced in ink on the dull side will make the tracing lie 
flat after removing from the board and not roll up, an objectionable 
feature caused by drawing on the smooth side. 

4. Heavy black lines are required on tracing cloth. (See 
thickness at middle of full line. Fig. 13.) Light, in printing, will 
burn through fine thin lines, causing a blue-print to appear blurred 
and indistinct. (Read ''Inking In," paragraph 3.) 

5. Lines on tracings are not shaded. 

6. Rule pencil guide lines when lettering a tracing and print 
all lettering without any attempt at tracing it. 



58 

7. Ink may be erased from tracing cloth, the pencil eraser 
usually being sufficient. The ink eraser should be used with care 
to avoid cutting the fabric. Place a triangle or other hard-surfaced 
article under the cloth when erasing. Wherever an erasure has 
been made, the place should be rubbed with a soapstone pencil 
or powdered chalk before re-inking to prevent the ink from passing 
through the cloth. The powder must be removed before the ink 
is applied. 

8. Ink dropped upon tracing cloth should never be blotted, 
but should be smeared as quickly as possible with the thumb, 
using a scooping-up motion. When the smear has dried it is 
readily erased with the pencil eraser. 

9. Pencil marks can be removed with the Art Gum cleaning 
rubber without affecting the ink lines. 

10. Trim tracings as directed, read paragraph 2 on Trimming. 

BLUE-PRINTS. 1. Original drawings are seldom sent into 
the shop. Duplicates in the shape of either blue-prints (white 
lines on a blue ground) or white prints (blue or black lines on a 
white ground) are used in place of them. 

2. These prints are moderate in cost and can be produced in 
endless numbers. They are obtained by exposing a sensitized 
paper or cloth to light rays. A positive tracing of the original 
drawing on a translucent medium, such as tracing cloth or paper, 
is interposed between a light and the sensitized paper and in 
direct contact with the latter, the time of exposure depending 
upon the intensity of the light and the composition of the sensitizing 
emulsion. 

3. The age, or length of time the paper has been sensitized, 
modifies the time of exposure. The fresher the paper, the less 
exposure required. The prints are fixed by immersing for about 
ten minutes in clear water. Special papers require the addition of 
chemicals to the fixing bath. Instructions for the treatment of 
such papers generally accompany them. 

4. Blue-Print Paper, and other sensitized papers, are obtain- 
able in different grades of stock and different weights. Light 
weight paper is used for prints that will require very little usage 
or for prints to be mailed. Heavy weight tough papers are used 
for prints requiring rough or frequent handling. 

GEARS. 1. Conventional lines and notations for spur and 
bevel gears will be found on Plates L and M. 

22. For the theory of gearing and method of drawing various 
types of gear wheels, refer to one of the many text books on the 
subject. George B. Grant's "Treatise on Gears," and Brown 



59 



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61 



8c Sharpens ''Practical Treatise on Gearing 
Gearing," are published by the manufacturers. 



and "Pormulag in 



SCREW THREADS. 1. A helix or screw curve is the path 
of a point moving on the surface of a circular cylinder, the motion 
of the point around the axis and paral- 
lel to the axis being uniform. 

2. The method of drawing the helix 
is shown in Fig. 42, the true shape of 
a V and a square thread being shown. 
When drawing screw threads, except 
for very large diameters, it is not 
necessary to lay down the curve of the 
helices of which they are comprised. 
Straight lines properly drawn from point 
to point and root to root answer all 
practical purposes. (See Fig. 43.) 

3. To draw a screw thread, lay off 
the pitch of the points accurately on 
one side. Draw shape of threads on 
that side. Locate any one point on 
opposite side. Draw the point line 
across, then draw all point lines parallel 
to this one. Draw shape of threads on 
opposite side. Draw root lines across. 
This is the quickest, most accurate and 
practical method. 

4. A right-hand thread is one that 
will cause a threaded piece to advance 
into a tapped hole when the piece is 
turned clockwise. (See Fig. 43.) 

5. A left-hand thread is one that 
will cause a threaded piece to advance 
into a tapped hole when the piece is 
turned counter-clockwise. (See Fig. 43.) 

6. If a threaded piece is held hori- 
zontally with the axis at right angles 

to the body, the threads seen will incline away from the body 
from left to right for a right-hand thread and from right to left for 
a left-hand thread. 

7. Threads are understood to be U. S. standard, single and 
right-hand unless otherwise specified. Standard shapes are 
shown in Plates N and O. 




■*-ROOT DI/\M.— I 

diam of screw 
Fig. 42. 



62 



RIGHT HAINID IN5IDL \ND OUTSIDE SCREW THREADS 
Sirsl3L_C V. DOUBL_E V. Sir-4Gl_E: 5Q. DOUBLE SQ. 




5irNaGi_E: v^. doublei v: 3irNiG\_E: sq. doub\—e: sq. 

LEFT HAMD INSIDE AND OUTSIDE SCREW THREADS 

Fig. 43. 

8. The pitch of a single thread is the distance between two 
adjacent points. It is the distance a point would advance parallel 
to the axis in one revolution of the thread (Fig. 42); e. g., single 
thread i" pitch, 4 pitch, or 4 threads per inch are the same. 

9. The lead of a double, triple or other multiple thread is 
the distance from one point to the next point of the same thread. 
(See Fig. 43.) The distance between two adjacent multiple 
threads is sometimes called the divided pitch. The lead is more 
generally specified. 

10. Multiple threads are noted thus: Double thread J" 
lead, or Double thread 2 pitch; Triple thread f" lead, or Triple 
thread 1| pitch. Triple thread 3 pitch, means three threads each 
making three revolutions per inch. 



63 



11. The diameter of a thread 
of the threaded portion of a piece. 

12. Screw threads 
in a section are drawn 
as shown in Fig. 44. 
Note that at B the point 
and root Hnes are not 
drawn across the section, 
and that those drawn at 
C and A are beyond the 
section. 

13. Hidden threads 
are always represented by 
parallel dotted Hnes. (See 
nuts, Fig. 17, hole, Fig. 45, 
and bolt in Fig. 46.) 



is the extreme outside diameter 

(See Fig. 42.) 




Fig. 44. 



TAPPED HOLES. 1. The diameter of a tapped (threaded) 
hole is the outside diameter of the threaded piece that would fit 

that hole, not R the 




0=DIAM OF TAP 

R = ROOT DIAM. 

D = DRILL DIAM. 

H=^ DEPTH DRILLED. 

T= DEPTH TAPPED. 
D=R, APPROXIMATELY 
HIDDEN THREADS ARE 
ALWAYS INDICATED A5 
SHOWN ATX, 



Fig. 45. 



the threads at the back of the hole 
direction to those in the portion cut away 

reference to Figs. 42, 43, 44 and 45 will make this clear. 



apparent diameter of the 
hole. (See Fig. 45.) 

2. Drill size for tap 
is the diameter of the 
hole which is drilled to 
prepare it for the tap and 
which leaves the proper 
amount of stock for 
threads. Drills have a 
conical point which is 
118° or, for all practical 
purposes on a drawing, 
120°. Fig. 45 shows the 
shape of the bottom of 
a hole which has been 
drilled. The hole in this 
case has not been tapped 
to its full depth. 

3. A section through 
a threaded hole shows 
inclined in the opposite 

A little thought with 



64 



4. Tapped holes are shown by two circles, the inner one 
full and the outer one half full and half dotted. (See Figs. 45 and 
46.) All threaded holes should have a note ,designatmg the size 
they are to be tapped, f " Tap means that the hole is to be tapped 
to take a screw f " in diameter. 

CONVENTIONAL THREADS. 1. This method of showing 
screw threads is to be used, for clearness and economy, when the 
diameter of a thread, as drawn, measures less than |" on straight 
threads (see Fig. 46) and less than 1" on pipe threads (see Plate S). 

2. Conventional threads are used to indicate threads of all 
types. It is not necessary that the number of conventional 
threads should correspond with the actual number of threads 

CONVENTIONAL THREADS 

RIG 




Fig. 46. 



on the piece. If the thread is other than the U. S. Standard, or 
if the number of threads does not correspond with the standard 
number for the given diameter, there should be a note to that 
effect, thus: '' ISthds per inch," " Square Threads 4 per inch," 
"Double Square Thread 2 pitch," "Triple V Thread \" Lead," 
" \" Pipe Thread," " Taper Thread 14 per inch, taper x in. per ft.," 
" Acme Thread 4 per inch." 

3. The spacing of conventional thread lines should be done 
by eye ; pencil lines may be drawn to limit the length of the heavy 
root lines. The inclination of the lines should be practically the 
same as though the thread were drawn out to its actual shape. 
That is, for a single thread a point on one side should be diametrically 
opposite the adjoining root. For a double thread the point on 
one side should be diametrically opposite the point of the next 



65 

thread. For triple threads the point on one side is diametrically 
opposite the next root but one. Fig. 43 will make this clear. 

4. Conventional threads are not to be used on a section show- 
ing two pieces screwed together and both cross-hatched, as A, 

Fig. 44, or on a section showing an isolated outside thread, as B, 
Fig. 44. Isolated inside threads, as C, Fig. 44, may be drawn 
conventionally as stated in Paragraph 1. 

CORED HOLES. 1. Cored, bored, counter-bored and coun- 
tersunk holes must be so noted, the method of doing this, and the 
required dimensions for each case, are shown in Fig. 47. 




Fig. 47. 



SCREW THREAD PROPORTIONS AND TABLES. The 

standard forms and proportions of screw threads in practical use 
in the United States will be found on Plates N and O. 

BOLTS. 1. The standard proportions for Bolt Threads, 
Heads and Nuts shown on Plate P and tabulated on Plate Q, 
were adopted by the Frankhn Institute, December, 1864. The 
sizes for bolt heads in Plate Q are a manufacturer's. 

2. Manufacturers have deviated slightly from these propor- 
tions, owing to the materials used in their manufacture not being 
commercial sizes. 

3. When drawing bolts and nuts, take dimensions from table 
on Plate Q and use the method shown on Plate P for approximaring 
the curves which are, in reahty, porrions of hyperbolas, the results 
of chamfering. 



66 



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•21$ 


< 


cvjlvS 


"Olt 




-IN 


(HliS 


ss 


Q. I 
< < 


H^ 


"lit 


(0|oO 


M^ 


-IM 


(Pl^S 


lOloO 


r:|i? 


-Oji 


-L < \ ±ooy-^>N\i 


g ^ § 

£L -loo Q^ 
in" 2 H 
Q - < 

J ^ T 


olS 

zox 


-|(\j 
t 


-I(\J 


^ 


't 


-l<vl 


-IN 


-It 


«<> 


fO 


J < 


MlrO 


— IM 
fOlfO 


'Oli? 








rO 










^ - 


N 




-IN 




CO 


-It 

m 


-1(\J 




1- 




^sV \ 


^^ 


II ,1 O lo u. " 

II « oil « J 


o u. o 
zox 


(D 


CO 


N. 


r- 


v5 


vS 


-|(VJ 


LA 


10 






?iS 


^l^J 


I0jv5 


^iS 


=l5 


2115 


qp{ 


-IN 


lOJflO 


^1 

H a 


NjCO 




-|C0 


-It 


«O|0O 


HcvJ 


^IcO 


<0|^ 


Hoo 


3 ^^ X 

< o ^ ^ 
. u 

— ' M -^ 




L Q 
ZOX 

h 





00 


ys 


^ 


ro 




- 


1 







^1^ 


~l^ 


(ni^ 

■«.lv9 


ri:! 


l^lS 


-l«0 


init 


:;i5 


•OIOQ 


Q. Z 
i< < 


-H 


■0!^ 


'njoo 


M? 


-N 


<n|iS 


lOlcO 


^? 


•^It 



67 



SQUARE THREAD 




/? = PITCH OF THREAD =1-^ NO. OF THREADS PER INCH. 
/^= DEPTH OF THREAD « ^/ A^ -^ 
Z7- OUTSIDE DIAM. 



y» EFFECTIVE DIAM. 


AT ROOT- D-^/? = Z?-/P 










DIAM OF 
SCREW 


^ 
-* 


5 


3 

d 


7 
/6 


2. 


5 
6 


3" 

4 


7 
8 


1 


'E 


'^ 


'1 


'i 


THREADS 
PER INCH 


lO 


9 


a 


7 


6 


4 


5- 


^k 


4 


32 


3i 


3 


3 


DIAM OF 
SCREW 


'1 


'1 


'i 


2. 


-4 


4 


-1 


3 


-i 


3i 


-1 


-f 




THREADS 

PER»NCH 


-i 


^2 


^i 


-k 


2 


2 


'1 


'1 


4 


'1 


'i 


'i 





ACME STANDARD THREAD 




/?= PITCH OF THREAD = l-r NO. OF THREADS PER INCH. 

Z>= OUTSIDE DIAM.OF SCREW. t7^= DIAM. OF SCREW AT ROOT. 



NUMBER OF 
THREADS 
PER INCH 


DEPTH OF 
THREAD 


/ 

WIDTH AT 
POINT 


1 


,5 100 


.3 707 


1/3 


.3850 


.2 780 


• 2 


.2eOO 


. 1853 


3 


.1 7G7 


. 1235 


4 


.1350 


.0327 


5 


.1 100 


.0741 


6 


.0933 


.0GI8 


7 


.0814 


.0529 


8 


.0725 


.0463 


3 


.0<i55 


.04I3 


lO 


.OhOO 


.037 1 



^= DEPTH OF THREAD 



2XN0.THDS.PER1N 

I 



4.01 



NO.OF THDSPERIN 



-,0Z 



.3yo7 



f=WmHAT P0INT=-^^^^ THDS.PER .N. 

TO DRAW THE ACME THREAD, FIRST 
LAYOFF THE SUCCESSIVE PITCHES, 
FROM THESE POINTS MARK OFF THE 
POINT WIDTHS /. THROUGH THE TWO 
SETS OF POINTS THUS FOUND 
DRAW LINES AT 30 AS SHOWN. 
THIS IS SUFFICIENTLY CLOSE FOR 
A DRAWING. 



Plate O. 




Plate P. 



69 



PROPORTIONS FOR U.S. STANDARD 

SCREW THREADS AND NUTS 

HOOPES AND TOWNSEND'S STANDARD S\ZES FOR BOL.T HEADS 


DIAM 

OF 

BOLT 

D 


BOLT THREADS 


NUTS 


HEADS 1 


THDS. 

PEH 

INCH 

N 


DIAM. 

AT 
ROOT 


AREA 

AT 
ROOT 

A 


THICK 
HEX. 
oa SQ. 

T 


HEX. 
LONG 
DIAM. 

C 


SQ. 
\_0^4G 
DIAM. 

c 


HEX.SQ. 
SHORT 
DIAM. 

F 


HEX. OK SQ. 


COUNTERSUMK 


SHORT 
DIAM. 


THICK 
H 


DIAM. 
K 


THICK' 
H 


1 
4- 


20 


.185- 


.026 


1 
>4- 


37 
<&4 


45 

64- 


1 
2 


3 
S 


3 
/6 


2 


1 
8 


5 


1 8 


.240 


.045 


5 
/6 


J / 
i6 


27 
32 


!_9 
3Z 


IS 


IS 
64 


9 
/6 


3 
/6 


3 
d 


1 ^ 


.234 


.067 


3 
8 


5_' 


63 

G4 


ii 
16 


3 
/6 


9 
32 


LI 

/6 


3 
16 


7 

re 


1 4 


.344 


.092 


7 
/6> 


7 
& 


, 7 
'64- 


Z5 

32. 


2J 
32 


2,1 
64- 


3 
4 


7 
/6 


1 

2 


1 3 


400 


.125 


\ 
Z. 




1 '^ 
'64 


1 
8 


3 
4- 


3 
8 


7 
8 


1 
4 


2L 


1 2 


.454 


./6I 


/6 


' 8 


,23 
'64 


31 
3Z 


27 
3Z 


27 
64 


IS 
16 


4- 


3 


1/ 


.507 


.201 


5 
8 


7. 


, 1 
' 2 


ifi 


15 
16 


15 
3Z 


'i 


1 
4 


4- 


10 


.620 


.30i 


2. 

4 


7 

' 16 


,49 
'64 


'i 


'i 


3 
16 


•i 


3 
8 


7 

a 


9 


•73/ 


.419 


7 

a 


,21 
' 3Z 


^3\ 


',i 


'if 


Zl 
3Z 


'1 


7 
/6 




a 


.83^ 


.S50 




, 7 

' a 


2 a 


'1 


'i 


3 
4- 


'1 


1 
2. 


, 1 

' 8 


7 


.940 


.693 


, 1 

'8 


2 3^a 


^?. 


i^l 


'M 


27 
32 


@ 


, 1 
'4- 


7 


1.0 cs 


.890 


'4 


2;f 


^g 


2 


'i 


15 
16 


'a 


<b 


l.KoO 


\.0S(o 


, 3 

'a 


^3^1 


^3^a 


^r. 


^ii 


1 1 
'32 


l-L 

' 2. 


Q> 


l.ZQ^ 


1.294 




-5 


^li 


2i 


^i 


, 1 

'a 


1 ^ 
8 


4 


1.389 


1.5/5 


'a 


-E 


^f 


-1 


-f. 


, 7 
'32 


\ 4- / 


1 ^ 
'4- 


5 


1.49 1 


1.746 


1 ^ 
'4- 


^4 


^s 


-1 


^1 


, 5 
'16 


\ 


7 


/ 








, 7 

•'a 


s 


1.616 


2.051 


, 7 
•a 


-it 


-si 


^H 


^f^ 


,13 

'32 


2 


H 


1.7 12 


2.301 


2 


3| 


-li 


-i 


3 


. \ 
2 


^— "^Z^ 




^i 


H 


1.962 


3.0 2 3 


^i 


^4 


-li 


3^ 


IRON SET SCREWS 


4 


4 


2.176 


3.7/8 


H 


4^ 


'H 


'1 


iiiin 


V 


^i 


4- 


2.426 


4-.622 


^1 


^e 


6 


4i 


-« L- 


vwvvvx 


1 


«H ■> 


3 


H 


2.629 


SA2.Q 


3 


^1 


s^^ 


^1 


REGULAR SQ. »- 


4EAD 


3i 


H 


2.879 


6.S09 


^i 


^/i 


7ii 


5 


CUP OR ROUND POINT 
THREADS U.S. STANDARD 
F~H, SAME AS DIAM.OF 
SCRENA/. ^ 
DIAMETERS FROM^ TO 1^*' 


3i 


^i 


3.100 


7.547 


4 


^.^. 


7|| 


4 


3^ 


3 


3.3 18 


8.64/ 


^1 


^M 


«i 


-1 


4 


3 


3.567 


9.993 


4 


-A 


«I4 


4 


\^ARIf 


iS FRC 


)MJ 


rro. 


lU 



Plate Q. 



70 



MACHINE SCREWS. 1. Standard machine screws are 

shown on Plate R. The values in the table are very close to the 
A. S. M. E. Standard. 

TAPERS. 1. When it is desired that two or more pieces 
shall fit tightly and at the same time be readily removable or 
adjustable for taking up wear, one or more of the pieces are made 
tapering. 

2. The necessary dimensions are those of the larger end, 
the length of the tapered portion and the taper per foot or fraction 
of an inch in a whole number of inches, i. e., I" in 5". (See Fig. 48.) 



Taper ^/r?. per Ft 




Taper —/n.per Ft. 

-v^^ Always ^/ue the 

lapsr per Ft _ 
/'/7 aaW/f/on to 
the c^imensions 
shoi/i^n 






3 



JT\T 



Fig. 48. 

3. On a tapered piece that does not fit anything, give the 
size at each end and its length. The rate of taper must not be 
given. 

4. There is no universal standard for tapers, different lines of 
work and different shops adopt tapers suitable to their require- 
ments. The following, used in locomotive practice, is a fair sample: 

Bolt Taper ^" in 12^ Boiler Taps \" in \V. 
Cross-head Pins i'' in 5". Brass Cock Plug 1\" in 12". 
Cross-head Key \" in 8". Cross-head End of Piston Rod Y' in 5". 
Connecting Rod, Stub Keys and Cotters \" in Yl" . 



71 



STANDARD MACHINE SCREWS 

AMERICAN SCREW COMPANY 




F^IL\_I5TER HCAD 






HFh- 



tS 



NO 



FUAT HEAD 



ROUND HEAD 



Fll_\_lSTER HEIAD 



2 

3 

-4 

5 

& 

7 

8 

9 

lO 

\2. 

14 

16 

18 

20 

24 
2G 
28 
30 



.0842 
.0973 
.1 105 
.I23& 
.1368 
• ISOO 
.1631 
.1763 
.1894 
.2158 
.2421 
.2684 
.2947 
.3210 
.3474 
.3737 
.4 GOO 
.4263 
A5Z6 



,1631 

,1894 

,2 158 

.2421 

.2684 

,2947 

,32IO 

,3474 

,373 7 

,4-263 

,4790 

,5316 

,5842 

,6368 

,6895 

,7421 

,7421 

7948 

,8474 



.0454 
.0530 
.0605 
.0681 
.0757 
.0832 
.030^ 
.0984 
.1059 
.12IO 
.1362 
.15 13 
.1665 
.1816 
.1967 
.21 18 
.1967 
.2118 
.2270 



.030 
.032 
.034 
.036 
.039 
.04 1 
.043 
.045 
.048 

.osa 

.057 
.061 
.066 
.070 
.075 
.079 
.084 
.OS8 
.093 



.0151 
.0177 
.0202 
.0227 
.0252 
.0277 
.0303 
.0328 
.0353 
.0403 
,0454 
.0504 
.055S 
,0G05 
.0656 
.0706 
.0656 
.0706 
.0757 



.1544 
.1786 
.2028 
.2270 
.2512 
,2 754 
.2996 
,3238 
,3480 

,39^^ 

,4364 
,48 O 6 
,5248 
.5690 
.6106 
.6522 
.6938 
.73 54 
.7770 



.0672 
.0746 
.0820 
.0894 
.0968 
.1042 
.1116 
.1 ISO 
.1264 
.1412 
.1560 
.1 708 
.1856 
.2004 
.2 152 
.2300 
.2448 
.2596 
.2744 



.O30 
.032 
.034 
.036 
.033 
.04 1 
.04 3 
.045 
.048 
.052 
.057 
.06I 

.070 
.075 
.079 
.084 
.088 
.093 



,0403 
,OA48 
,0492 
,0536 
,0580 
,0625 
.0670 
,0714 
.0 75S 
,0847 
.0936 
.I024 
.1 I 14 
.1202 
.1291 
.I380 
.1469 
.1558 
.1646 



.1 350 
.1561 
.1772 
.1984 
.2195 
.2406 
.2617 
.2828 
.3040 
.3462 
.3884 
.4307 
.4729 
.5152 
.5574 
.5996 
.6419 
.6841 
.7264 



.054 9 
.0634 
.0720 
.08 06 
.0892 
.0978 
.I063 
.1 149 
.1235 
.1407 
.1578 
. I 750 
.1921 
.2093 
.2 267 
.2436 
.2608 
.2779 
,2951 



.01 26 
.0146 
.01 66 
.0186 
.0205 
.OZZ5 
,02LA5 
.0265 
.0285 
.0324 
.0364 
.0403 
.0443 
.0483 
.052O 
.0562 
.060I 
.0641 
.0681 



,030 
.032 
.034 
,036 
,039 
.04» 
,043 
.045 
.048 
,052. 
,057 
OGI 
,066 
070 
075 
073 
084 
088 
093 



.0338 
.039O 
.0443 
.049 6 
.0549 
.0602 
.0654 
.0707 
.0760 
.0866 
.097/ 
.1077 
.1 182 
.1288 
.1384 
.1499 
.I6O5 
.1710 
.1816 



MACHINE SCREWS ARE DESIGNATED THUS-^l2x£0 FILLISTER 
HEAD MACHINE SCREWS '' WHICH MEANS SIZE CeAUeE)*'ia HAVING 
20 THREADS PER INCH THEREON. SEE LAST COL-UMN IN THE 
TABLE OF STANDARDS FOR WIRE GAUGES. 

THE NUMBER OF THREADS PER INCH FOR THE VARIOUS SIZES 

WILL BE rOUND IN THE FOLLOWING TABLE. 



2 
3 
4 
5 
& 
7 
8 
9 
10 



THREADS PEIR INCH 



56 
56 



4© 
48 



40 
40 



36 
36 
36 



36 



32 
32 
32 
32 
iZ 
32 
32 



50 
30 
30 
30 
30 



£4 
24 



NO 



THREADS PER INCH 



1 2 


24 


20 


. . 


. . 




14 


24 


20 


1 8 


, . 




1 6 




20 


Id 


1 6 




18 




20 


18 


1 6 




20 






1 8 


1 6 




22 






18 


16 




24 






1 8 


1 6 


14 


26 






. . 


1 6 


14 


26 






. . 


1 6 


14 


30 




• • 




16 


14 



Plate R. 



72 



STANDARD STEEL TAPER PINS. 1. These pins, made 
by Pratt and Whitney Co.. taper J" per foot, and lengths vary by i". 



Size Xo. 

Large Diam. 0.156 
Length |-1 



0.172 



0.19.^ 



0.219 

3 , 3 



4 

0.250 

1-2 



5 
0.289 

A. ■i ± 



6 
0.341 
a-3i 



0.409 



8 9 10 

0.492 0.591 0.706 
lx-47 ih-Sr li-6 



PIPE. 1. Iron pipe is always specified by its nominal 
internal diameter. By referring to the pipe table it will be seen 
that the actual sizes differ from the nominal. Use actual sizes 
on drawings. (See Plate S.) 

2. A pipe tapped hole is shown in plan by two circles, the 
inner one being full and equal to the drill size, the outer one half 
full and half dotted and equal to the outside diameter of the pipe. 
(See illustration on Plate S.) 

3. Tubes of iron, steel, brass, copper, etc., are specified by 
their outside diameter and a gauge number for the thickness of 
the material, thus: 2" brass tube, 12 B. & S. gauge. 

STANDARD GAUGES. 1. Standard gauges for Wire, Plate 
and Screws are given in Plate T. 

WEIGHTS OF CASTINGS AND FORGINGS. 1. The 
approximate weight of a piece Is often required, especially for 
making estimates of cost from drawings. This is done by finding 
the volume and multiplying by the specific weight of the material 
of which it is to be made. As results within 10 per cent of actual 
weight are considered satisfactor}' in practice, it is not necessar}' 
to consider small fillets and other minute details. 

2. Assume the piece divided into a number of parts, the 
volumes of which are readily obtainable. From these the total 
volume and weight may be found. If close estimating is required 
and there are numerous fillets of some size, they should be taken 
into account. See Fig. 49 for the method of finding areas of fillets 
and round corners. 

WEIGHTS or METAL_S 



BRASS 

bromzie: and correir 

CAST IROtNi 

CAST STEIEIL. 

LEZAD 

WROUGHT IRON AND STEEL. 



WEISMS .09^^ PER CU. IN. 

« .2 6 « ^ 

M , ZB " » 

n .za^ '/ « 




LET A = AREIA OF CROSS SE:CT\0N OF A FlUV-EIT 

•4- 



C=R 



I - ras-^-J 



.ai^GR 



.Z R, APPROXIMATEL.r 



Fig. 49. 



73 



^'piPE-^ V//////A 






CONVENTIONAL METHOD TO BE 


JT 


li 




1 1 


~t± 


USED WHEN D, AFTER BE\NG 


A 






1 


-\ r^ unf\yvr^ lu c>q;m>ue., Mt./N:>URfe:> | 


u 


HH 


^y 7 


U^^ 


— hH 


LESS THAN ONE INCH. 


\ 


M///A 






PIPE THREAD TAPERS 1 IN 32 TO AXIS. 


THREAD GO) 












^ 


W^^M^M^^M^ 


OrJ INDIAM." 
PER FOOT. 




.^^ 


I i__ttM 


^^^^^is 


m$^^mmmm 


i.os" 

i 


5« 






THREA 
AS SHOV 
.ACTUAL 
THE TV- 
FURTHE 


DS 
VN. 
-LY __ 


If ■ 


^>\ 


11 ^ 


Z 


d 
S 




ip5. 
:sT 


V V ^ \ XJ 


M-i — ilj 


j 


L 




FROM END 
ARE NOT 
PERFECT, 
SEE TABLE. '■ 


^ P\ PE TA!^ L. H THD ^ 


^^M^fe$$^^^ 


lAuSMM^ 


^p\PE.^^ \ 


^^^^^ 










1 


WROUGHT IRON STEAM, GA5 AND WATER PIPE 


NATIONAL TUBE COMPANY— STAMOARD DIMENSVONS 


DIAMEITE-RS 


TRANSVERSE 

INTERNAL. 

AREAS 


THRE.ADS 


DRILL 
HOLE 
FOR 
TAP 


NOMINAL 
INTERNAL 


ACTUAL 


INTERNAL- 


EXTER 
NAL 


NO 
PER 


LENGTH 
THREADED 


LENGTH 
PERFECT 


STAN 


I EXTRA 


STAN 


EXTRA 




DARC 


) HEAVY 




DARD 


HEAVY 


INCH 


AT ROOT 




'/8 


27 


.205 


.405 


.05 7 


.03 3 


27 


% 


% 


^^ 


y^ 


.36- 


4 294 


.54 


.i04 


.068 


18 


% 


%z 


% 


% 


.49- 


i- .42 1 


.675 


.191 


.1 33 


18 


\ 


'%, 


'^33 


>a 


.62 


3 .542 


.84 


304- 


.231 


14 


'k 


% 


^^3e 


% 


.82' 


4- .736 


1.050 


.53 3 


.425 


14 


% 


% 


'^6 


1 


1.04 


8 .95 1 


1.3 J 5 


86 1 


.7/ 


M'/2 


\ 


'4 


/^. 


'i 


/.3S 


O 1.272 


1.660 


1.496 


1.271 


11-4 


"4 


'%* 


1% 


l^a 


/.<&/ 


1 1.4 94 


I.900 


2.03C 


1.753 


i.'4 


'\ 


y,^ 


'% 


2 


2.0 6 


7 i.333 


2.375 


3.356 


2.9 35 


.!•/, 


% 


"lU 


2^6 


2^ 


2.4 6 


8 2.3 15 


2.875 


4-.780 


4.2 09 


8 


1 


% 


2'i^ 


3 


3.0 6 


7 2.892 


3.500 


7.383 


6.563 


6 


1 


'% 


3f. 


^!', 


3.54 


8 3.358 


4,000 


9.887 


8.856 


8 


1'/,^ 


1 


3% 


4 


4.0 2 


6 3.8 1 8 


4.500 


1 2.730 


1 1.449 


8 


''/8 


i5U 


4^^ 


^\ 


4.5 O 


8 4-.a8o 


5.000 


15.961 


I4-.3S7 


8 


''4 


<y<^ 


4% 


5 


5.04 


5 4.81 3 


5.5-6 3 


19.986 


18.193 


8 


I'A 


l%2 


^^8 


G 


6.0 6 


5 5.75/ 


6.6 25 


2 8.886 


2 5.976 


8 


'% 


''4 


<^^^ 


7 


7.0 2 


3 6.625 


7.6 25 


3 8.7^3 


3-+.-*-7 2 


8 


I'k 


!'/» 


7^. 


8 


7.98 


2 7625 


8.6 25 


5 O.O 2 1 


45.664 


8 


1% 


^\ 


8^^ 


3 


8.9 3 


7 8.625 


9.6 2 5 


62.722 


58.426 


8 


1% 


1'//* 


3^8 


lO 


/O.OI 


9 9.750 


lOJSO 


78.822 


74.662 


8 


1% 


('& 


'-^ 


1 1 


1 I.OO 
1 2.00 


.. 


n.iso 

/2.750 


9 5.034- 
//3.090 




8 
8 


1% 
1% 


1% 
1% 




I I.J50 


108.43 



Plate S. 



74 



STANDARDS FOR.WiRE GAUGES 


5 


IN USE iN THE UNITED 


STATES 


DiMELNS 


IONS >\'^E IN DEC'V!A'^ i=&R-S C^ 


^s sc- 


1? 

1^' 


^' 
c < 

II 


Z Z tr 

at 


pi 

5 r z 

±^ ui 


si 

H 


P 


E £ - 
LJ C w 

III 

Z U 


oooocc 

00000 








.4375 


000000 

ocooc 




1..."... 


00 


.46 ' 


.454- 




.-^063 


0000 




coc 


.4096 


.425 




.3 75-0 


000 


.03 , 5 


CO 


.36^6 


.38 




.34.33 


00 


04.4.7 





.3249 


.54. 




.3. 25 





0578 


i 


.2893 


.3 


.2 27 


.2813 


1 


07 iO 


2 


.2576 


.2 84 


.2 13 


.2656 


2 


0S42 


3 


.2294. 


.259 


.2 12 


.25 


3 


0973 


4 


.204-3 


238 


.207 


.2344 


4 


.. 1 05 


5 


.18 19 


.22 


.204 


.2188 


^ 


. (236 


6 


. 1 620 


.203 


.201 


.2031 


6 


. i 368 


7 


.i443 


.18 


.1 99 


.1875^ 


7 


.1500 


8 


.I28S 


.1 65 


.137 


.1719 


8 


.1 631 


3 


• f 14-4 


.lAB 


.134 


.1563 


3 


.1763 


to 


.lOIS 


.134 


131 


.I406 


10 


. : 894.- 


1 1 


.0307 


.12 


.iSd 


.1 25 


II 


.2026 


12 


.0808 


./OS 


.185 


.1 034 


12 


.2 58 


13 


.0720 


.035 


.182 


.0938 


13 


.2289 


14 


.064-1 


.053 


.ISO 


•OTSI 


14 


.242. 


15 


.057( 


.OIZ 


.178 


.0703 


15 


.Zc-SZ 


16 


.0508 


.065 


.175 


.0625 


16 


.2 6 6-* 


17 


.0453 


.058 


.172 


.0563 


17 


.25:6 


18 


.0403 


.049 


.163 


.05 


18 


.254-7 


13 


.0359 


.04-2 


.1 6^ 


.04.38 


13 


.3079 


20 


.0320 


.035 


.1 6 i 


.0275 


20 


.32 i 


2 1 


.0285 


.032 


.15- 


.0 344 


2 1 


.33^2 


22 


.0252 


.028 


.155 


.03 i 3 


22 


.3474 


23 


.0226 


.025 


,153 


.02SI 


23 


.3605 


24 


.020 1 


.022 


.\51 


.025 


24 


-3737 


2S 


.Ol 79 


' .02 


• I'^a 


.OZ /9 


ZS 


2868 


26 


.OJ 53 


.01 e 


.1 46 


.0. 88 


26 


.4000 


27 


.O i42 


.0\ 6 


.14-3 


.0; T2 


27 


.^1 32 


28 


.0 \ 26 


.0 14 


.1 39 


.0/56 


28 


4-263 


29 


.O ! 3 


.Ol 3 


.13 4 


.0 140 


29 


.A 355 


3C 


. C I C 


.0 12 


.12 7 


.01 25 


30 


<r5Z& 


3 1 


.0083 


.O 1 


.120 


.0/ 09 


3 ^ 


4^53 


32 


.OO&O 


.0 03 


.1 15 


.01 OZ 


32 


4.73C 


33 


.001 : 


.008 


J 12 


.003^ 


33 


^3Z , 


3^ 


.0063 


.C07 


.1 I c 


.0086 


3^ 


. 5C 5 3 


35 


.005^ 


.0 05 


.1 08 


.0078 


35 


.5 64 


3fc 


.005 


.004 


.106 


.GOTO 


3& 


.536 


37 


.004-5 


... 


.103 


.0066 


37 


.544-8 


38 


.O040 




.1 01 


.0063 


38 
39 


.5579 


33 


.003S 




.099 




,57 1 i 


40 


.0031 




.037 




40 


.584-Z' 





Plate T. 



75 



SEQMETR 




TO INSCRIBE A PENTAGON 
IN A GIVEN CIRCLE. 

^4 Bisect the rac/ZusatR 
D With /fas cr ce/^f^^r- 

eyifrt: OH 7?^e cora^Oh 
'^w///^re/:> off s f//77e5 



C DRAWING 



TO CONSTRUCT ANY POLYGON 
ON A GIVEN LINE -CO. 
-^^ Dns^\^/c7/nc wit/7 CD 
c?s K<^c?/ius. c/j\^/c/e // 
V^^^\^c^ j^//7/o scfm^ A/o. parts 
as /:>o/y^or? has s/c/es. 




t6 lay off an arc equal to 
le , j& length of strai6h7 

LIME Di\/ic/e//>7e^S 
'//7to '^e^4/a//Darfs, 
fro/r? '^'^^/00//7f£ 
,c//z7t^ arc B D. 
,j^^:^^^ ' Le/7^//7 y^Dofi^^rc 
/'s e<^i^a//^f/7<^/h of^/iAS/7^i9^^3. 



TO DRAW/ A CIRCULAR ARC 

,G _ THROUGH 3 POINTS /\BP. 

'-* ah7i^ tyres Ce& AH. 

f^ Dn7(/Vy^Bto3c9r7c/ 

^ CSfoa. Divia/eCS 

^1 ^AS//?fo £^. //o./ffor- 

fs^ ca^//>?e/e/c 6ii/<. 





TO CONSTRUCT A PARABOLA 

-^3? ! ^ / 2 34- S/oaj^S/?/se ^/i/&^. 
.(;fDiv/a/e /her/se '4c/ 
X L^//7/o e^e/a//DarAs 
\V" af/7a/04-//?fo sa/^e 
^-C ^?c//f7jber: Jom7C^6^ 
ydcic/w/fhO //ffer- 
s^ct/j^^ v^r//ca/s art/Go)/7ts /9ei^k 




TO CONSTRVJCTA HYBERBOLA 

Siver? frt7/7SveKse, 
' crxis^S c?^a</oc/£/: 
Tl ^ Ja/re any/Do/nts 
V.f }} /^2. 4 o^a^x/s F3. 
M7Ae fa^A/a^a^/a=Bi. 

/=yo/S(//^C/^/?f/:?o/>^fs, 




TO ORAVVJ AN ACCURATE ELLIPSE 
BOTH AXE:S G5VEN 

Drc^vy c/rc/^s w//h 
/^T^orax/sA/A^ d? 
' ^^/J^arc^XAsAt/^as 




TO DRAW/ APPROXIMATE ELLIPSE 

_N| L. 



DAa/p9S, Z)rx9t^/z^tafij/ 
/sat )/S//A^o//ro/^^&Zi 



TO DRAW A SPIRAL layoff The 

e ^/f r-crcy/us f/ec/or^ 

//? cy//^r&/7 -t 

,gr /ifos/f/o^^sat 

<^^uay/cy/^yAps 

\ > \cyj'9a/cy>Wa^«s/f 

I \ \ /y?fo &^£^£^/ 




Afa/re OL'C/a! OT-^/^/^ 




jtksrr-jf^oy/^^z^, {/////? ^ Z c:/n:7iA/ 



TO^bRA\A/A -^CENTER SPIRAL 

Coy^tr(/cfc^Si^e/t7n 
^ /234\/\A/thsun7of 
sic/es ei^c^a/ff/e 
joi/ch /-C cf'r^cf 
yOKo/o/7<^ sic/es in 
o/'7& c9i^r-ffa//or7. 
^rc:/^ ^3a'rc^A> 




TO DRAW A CYCLOID. 07i?^^e 



TO DRAW/ AN INVOLUTE 
5-432 I O 




Dra^rtv oela/^. 
foD/c7/^.Oa 
c?j*^c/ ef^^a/ 
yo ser^/c/f^ 



'C(y/^fere/9C^, 

^Afa/reOAanrOi 

^^/TB^A?, fo C/e/c 





EPICYCLOID 

£>f'i//a<e raAA/fy 
p^a/j^/e///- 
fo e^c/a/ 

Grrtr/ffc7>^ 
P^<Da=a/^o^ 



TO DRAW A HYPOCYCublD. U/l//cte 

5 .-iAK ro/A/A^^cyi^'cr/s^/i^/o 
e(^c/c7/ytyar/s 0//Z, 
^ Z3efc cy/^a^y*^^t7Are 
AA^ehase c:yirt:A€ 
, £yrcs Ocs^ cy/p 
'e^c/a/ arcs 
"o/ /2 etc. 




Plate U. 



76 



DECIMALS OF AN INCH FOR EACH 64 


Tm 


32nos 


64ths. 


DECIMAL 


FRACTION 


32nds. 


64ths. 


DECIMAL 


FRACTION 




1 


.015625 






33 


515625 




1 


2 


.03I25 




17 


34 


.53125 






3 


.046875 






3S 


.5-4^875 




2. 


4 


.0625 


1-16 


Id 


36 


.5*625 


9-16 




5 


.078I2 5 






37 


.57&{Z5 




3 


6 


.09375 




19 


38 


.59375 






7 


.I09375 






39 


.609375 




A 


8 


.125 


1-8 


20 


40 


.625 


5-8 




9 


.I40625 






41 


.640625 




5" 


10 


.15625 




21 


42 


.65625 






1 1 


.171875' 






AZ 


.671875 




6 


12 


.1875 


3-16 


22 


44 


.6875- 


11-16 




13 


.203125 






45 


.703I25 




7 


14 


.2 1875 




23 


46 


.71875 






IS 


.234375 






47 


.734375 




8 


16 


.25 


1-4 


24 


48 


.75 


3-4 




17 


.265625 






49 


.V65625 




9 


18 


.28125 




25 


50 


.78125 






19 


.296875 






51 


.ysesTS 




10 


20 


.3125 


5-16 


26 


52 


.8125 


13-16 




2 1 


.328125" 






53 


.828125 




1 1 


22 


.34375 




27 


5A 


.84375 






23 


.359375 






55 


.859375 




12 


24 


.375- 


3-8 


28 


56 


.875 


7-8 




25 


.390625 






57 


.890625 




13 


26 


.4062 5 




29 


SB 


.90625 






27 


.42/875 






59 


.921875 




14 


28 


.4375 


7-16 


30 


60 


.9375 


15-16 




29 


.453125 






61 


.953125 




15 


30 


.46875 




31 


62 


.96875 






3 1 


.484375 






63 


.984375 




16 


32 


.5 


1-2 


32 


64 


1. 


1 



Plate X. 



77 

CHECKING. 1. A Mechanical Drawing is always checked 
for errors, omissions and correctness in representation before it 
reaches the artisan. 

2. The draftsman should check his work for his own satis- 
faction and protection. 

3. A drawing should be checked by some one familiar with 
the requirements other than the draftsman that made it, to avoid 
costly mistakes, doubtful meaning and impractical construction. 

4. Drawings are corrected to make them right and explicit. 

5. Erasing and making corrections on a drawing is easier and 
cheaper than making alterations on a piece in the shops — it keeps 
things from going to the scrap pile. 

y/ Check MARK- o,H. 

^ Draw A CENTER LINE 

,r\^r^^^->^^^ ^ ^-^ Erase the line 

— X:X-?^^-7< — Draw A squd l/ne 

/Hill II //I /I //M/i M Dot the l/ne 

■5 MS — - Shade une - No shade l/ne 

/^6L//?ES,^RROlM5 ETC O/^/TTED 
D/ME/VS/ON /S /NCORREC T 

^ Take out— Useless 

? M£AN//\/C? /S NOT CLEAR 



po 




Z 



Oi; 




>r F/y- GiyE TH/S A ttention 

Fig. 50. 

6. Check a drawing for the following features and make the 
required changes. (See Checker's Symbols, Fig. 50.) 

Clearness. — Is it easy to read and understand? 

Are the lines correct in weight and punctuation? 
Views. — Are they correctly projected from each other? 

Do they show the object completely? 

Would others show the object to better advantage? 
Sections. — Are they drawn correctly and their locations indicated? 

Are others needed to show the construction? 
Dimensions. — Are the values correct by scale or calculations? 

Are enough given for complete information and no repetitions? 

Are necessary ones given without resort to addition and sub- 
traction ? 

Are they the ones wanted and properly placed for usefulness? 



Motions. — Do moving parts have proper clearance' 
Fastenings. — Can they be readily put in place and removed' 
Lettering. — Are all required symbols for Finish, Fit and Identifica- 
tion given' 

Has all material been correctly specified' 

Are all necessary notes given ' 

Does the title contain the necessary and correct information' 

Is the index number, for filing and identification correct ^ 
Design. — Is the design practical and of pleasing appearance? 

See Practical Points in ^Mechanical Design Drawing. 

DESIGNING. 1. A mechanical scheme may originate in the 
mind without a demand for it or the idea may have to be evolved 
b}' the pressure of necessity : in the latter case considerable design- 
ing is required. 

2. A design is developed by analytical and empirical methods 
augmented by the designer's mechanical sense of proportions. 

3. Analytical design involves the determination of dimensions 
by mathematical formulas, deducted from scientific theories and 
tests which the designer should understand. 

4. Empirical design is determining size by formulas and pro- 
portions based on experience or obser^'ation. 

5. Mechanical sense of proportion is that ability which enables 
one to design the thing required, using previously determined sizes 
or quantities to build around. 

6. The procedure in Mechanical Design should be about as 
follows ; 

A SCHEDULE 



8. 
9. 

10. 



-scheme sketches, 
involving forces. 



The thing required. 

Specifications to be met. 

General scheme of layout- 
Analysis and calculations 
velocities, friction, etc. 

2^Iemorandum sketches for dim^ensions and 
quantities calculated. 

Empirical proportioning of parts. 

Standard proportions of parts. 

Mechanical sense of proportions. 

Layout of main center lines, base lines, clear- 
ance and reference lines. 



Drawing the design accurately 
order. 



and 



in logical 



Subject 

Given 

Required 

Scheme 

Alechanism 

Assumptions 

Analysis 

Procedure 

Formulate 

Calculate 

Result 

Deductions 

Conclusions 

Drawing 



I 

I 



79 

7. Mechanical design drawing requires a full knowledge of 
Mechanical Drawing, the Theory of Design and Shop Methods of 
Construction. Many practical points must be observed. 

8. Practical points to observe in designing: 

Keep notes, in loose-leaf form, in a neat and logical order, of all 

sketches, calculations and memoranda. 
Be systematic in designing and drawing; it is the shortest and 

best way to get results. 
Freehand sketches make good memoranda as the work progresses. 
Views and sections to make a clear and workable drawing. 
Cost of construction and ease of operation are controlled by the 

designer. 
Take no risks in proportioning parts where their safe size can be 

calculated. 
Assume something reasonable and test its fitness by calculation or 

graphical trial. 
Think of the construction and machining of the parts as the 

drawing progresses — impractical and impossible -design should 

be avoided. 
The general appearance should be pleasing, not ugly. 
Things that are right look right — is true. 
Erecting must be done with the least effort. 

Dismantling for cleaning or replacements should be the least possible. 
Take a machine apart mentally while drawing it. 
Adjustment for wear must be provided and accessible for take-up. 
Adjustment for centering should be provided when necessary. 
Centering and lining up must be provided for by pins or projections 

in recesses. 
Parts should be few in number, especially those to be replaced. 
Moving parts must not foul anything; leave plenty of clearance. 
Right and left-hand parts should be avoided; they are not inter- 
changeable. 
Minor details omitted cause delay, inconvenience and expense. 
Non-essentials should be omitted from the design — aim for 

simplicity. 
Thin ribs will crack if adjoining wall is quite thick. 
Fillets must be shown; sharp corners are weak and undesirable. 
Round edges must be shown where required. 
Oil holes and grooves must be provided and be easy to reach. 
Standard fastenings, fittings and parts should be used to reduce 

costs. 
Through bolts are preferred to studs and studs to cap bolts. 
Bolts should have room for inserting and forced removal. 



I 



80 

Nuts and cap bolts must be free to turn when near fillets, ribs or 
walls. 

Check nuts or cotter pins should be specified where needed. 

Machine screws are preferable to bolts on small work. 

Set screws should be used for holding parts in place, not for trans- 
mitting any considerable force. 

Keys are fastenings used to transmit appreciable force. 

Keys should have room for inserting and be easy to remove. 

Tapering cotters are fastenings used where adjustment and quick 
release are required. 



INDEX. 



PAGE 

Abbreviations — Fig. 20 23 

Arrangement of Views — Fig. 10, Fig. 

11 13 

Arrow Heads— Fig. 18, Fig. 19 20 

Assembly Drawings 57 

Bill of Materials— Plates H,J 51 

Blue-prints 58 

Bolts— Plates P, Q 65 

Checking— Fig. 50 77 

Classification of Drawings 4 

Conventional Threads — Fig. 46 64 

Cored Holes— Fig. 47 65 

Cross-hatching— Plate A, Fig. 24 25 

Decimal Equivalents — Plate X. 76 

Designing 78 

Developments — Fig. 29 39 

Dimensioning — Fig. 18, Fig. 19 20 

Eerecting Drawings 57 

Essentials .' 4 

Figures — Fig. 18 20 

Finish Marks— Fig. 21 23 

Finished Surfaces 24 

Fitting Symbols— Fig. 22 24 

Fractions — Fig. 18 21 

Gears — Plates L, M 58 

Geometric Drawing — Plate U 75 

Inking In 19 

Instruments — Fig. 1 , Fig. 2 5 

Intersections — Fig. 26, Fig. 27, Fig. 28 35 

Laying out Views — Fig. 12 14 

Isometric Drawing — Figs. 30, 31, 32, 

33, 34, 35, 36, 37 40 

Lettering, Fig. 40,* Fig. 41, Plates E. F 49 



PAGE 

Line Shading— Fig. 25, Plates B, C, D 29 

Lines— Fig. 13, Fig. 14, Fig. 15 15 

Machine Screws — Plate R 70 

Number Circle — Fig. 4, Fig. 5 7 

Omitted Dimensions 22 

Pipes and Tubes— Plate S 2 

Preface 3 

Projection — Fig. 9 10 

vScales 13 

Screw Threads— Fig. 42, Fig. 43, 

Fig. 44 61 

Screw Threads. Proportions and 

Tables— Plates N, O 65 

Sections— Fig. 17, Fig. 23 24 

Shade Lines— Fig. 16 19 

Size of Sheets— Fig. 6, Fig. 7, Fig. 8 . 8 

Size of Tracings— Fig. 8 8 

Sketching— Fig. 38, Fig. 39 44 

Standard Wire Gauges— Plate T 74 

Sub-Captions— Plate H, I 51 

Tabulated Dimensions — Plate 1 22 

Tapers— Fig. 48 70 

Taper Pins, Standard 72 

Tapped Holes — Fig. 45 63 

Tinting 28 

Titles— Plates G, H, J, K 51 

Tracings 57 

Trimming Drawings 10 

Use of Instruments — Fig. 3 6 

Weights of Castings and Forgings — 

Fig. 49 72 

Wire and Screw Gauges — Plate T 74 



(81) 



LIST OF ILLUSTRATIONS, 



FIGURE PAGE 

1 — Instruments in Case 5 

2 — Irregular Curve 6 

3— Use of Triangles . 6 

4 — Xumber Circle 7 

5 — Part Xumber Circle 7 

6 — Size of Sheets. Form 1 S 

7 — Size of Sheets, Forms 2 and 3 . . . . 9 

8— Size of Sheets. Form 4 9 

9 — Projection Planes 11 

10 — Object Surrounded by Planes . . . . 12 

1 1 — Position of Views 12 

1 2 — Laying out views 14 

1 3 — Lines ( Samples of) 15 

14 — Dotted Lines. (Ending) 15 

15 — Piston (Contrast of Lines) 16 

1 6 — Shade Lines IS 

17 — Coupling (L"se of Lines) 17 

18 — Size of Figures and Arrows 20 

1 9 — Dimensioning Small Spaces 21 

20 — Abbreviations and Symbols 23 

21— Finish Marks 23 

22 — Fitting Symbols 24 

23 — Section Planes 25 

24 — Breaks in Long Pieces 27 

25 — Line Shading (Theor\- ; 30 

26 — Intersection of Cylinders 35 

27 — Intersection of Elbow and Cyl- 
inder 36 

28 — Intersection of Bell Shaped Sur- 
face and Plane 38 

29 — Development of Surfaces 39 

30 — Isometric Projection (Theory) .... 40 

31 — Isometric Projection (Theor\^) .... 40 

32 — Isom.etric Projection (Theorv^j . . . 41 

33 — Isometric Axes and Planes 41 

34 — Isometric Projection of Circles ... 42 

35 — Isometric Plotting 43 

36 — Isometric Projection of a Circle . . 43 

37 — Isometric Drawing 43 

38 — Sketch 45 

39— Sketch (Details) 47 



FIGURE PAGE 

40 — Block Letters 49 

41— Ruled Letters 49 

42— Screw Thread. (Helix) 61 

43— Screw Threads. (R & L, V 

&Sq.) 62 

44 — Section Through Threads 63 

45 — Tapped Hole 63 

46 — Conventional Threads 64 

47 — Holes (Cored and Bored) 65 

48 — Tapers 70 

49— Weights of Metals 72 

50 — Checkers' Svmbols 77 



PLATE 

A — Con\-entional Standard Cross- 
hatchings 26 

B — Line Shading. (Examples) 32 

C — Line Shading. " 33 

D — Line Shading. " 34 

E — Freehand Letters 48 

F — Lettering. (Heights) 50 

G — Titles. (General) 52 

H — Titles, Sub-Captions, Bill of 

Materials 53 

I — Tabulated Dimensions 54 

J — Titles. (Manufacturers) 55 

K— Titles. (Design) 56 

L — Drawing the Involute Tooth 59 

M — Drawing Bevel Gears 60 

N— U. S. & V. Standard Threads. 

(Proportions) 66 

O — Square and Acme Standard 

Threads (Proportions) 67 

P — Bolt Heads and Xuts 68 

Q— U. S. Screw Threads and Xuts. ... 69 

R — Machine Screws . .r 71 

S — Pipe Treads, Table of Sizes 73 

T — Wire and Screw Gauges 74 

L^ — Geometric Drawing 75 

X — Decimal Equivalents 76 



^82) 



» 



I 



^^^^^s 



LIBRARY OF CONGRESS^ \'-\'i] 



019 970 356 




iiililllllp 


















